xxreal_1.miz



    begin

    reserve x for set,

p,q,r,s,t,u for ExtReal,

g for Real,

a for Element of ExtREAL ;

    scheme :: XXREAL_1:sch1

    Conti { P,Q[ object] } :

ex s st (for r st P[r] holds r <= s) & for r st Q[r] holds s <= r

      provided

       A1: for r, s st P[r] & Q[s] holds r <= s;

      set A = { a : P[a] }, B = { a : Q[a] };

      reconsider X = (A /\ REAL ), Y = (B /\ REAL ) as Subset of REAL by XBOOLE_1: 17;

      per cases ;

        suppose

         A2: X = {} ;

        per cases ;

          suppose

           A3: +infty in A;

          take +infty ;

          thus for r st P[r] holds r <= +infty by XXREAL_0: 3;

          ex a st a = +infty & P[a] by A3;

          hence thesis by A1;

        end;

          suppose

           A4: not +infty in A;

          take -infty ;

          thus for r st P[r] holds r <= -infty

          proof

            let r such that

             A5: P[r];

            r in ExtREAL by XXREAL_0:def 1;

            then

             A6: r in A by A5;

            per cases by A4, A6, XXREAL_0: 14;

              suppose r = -infty ;

              hence thesis;

            end;

              suppose r in REAL ;

              hence thesis by A2, A6, XBOOLE_0:def 4;

            end;

          end;

          thus thesis by XXREAL_0: 5;

        end;

      end;

        suppose

         A7: Y = {} ;

        per cases ;

          suppose

           A8: -infty in B;

          take -infty ;

          ex a st a = -infty & Q[a] by A8;

          hence for r st P[r] holds r <= -infty by A1;

          thus thesis by XXREAL_0: 5;

        end;

          suppose

           A9: not -infty in B;

          take +infty ;

          thus for r st P[r] holds r <= +infty by XXREAL_0: 3;

          let r such that

           A10: Q[r];

          r in ExtREAL by XXREAL_0:def 1;

          then

           A11: r in B by A10;

          per cases by A9, A11, XXREAL_0: 14;

            suppose r = +infty ;

            hence thesis;

          end;

            suppose r in REAL ;

            hence thesis by A7, A11, XBOOLE_0:def 4;

          end;

        end;

      end;

        suppose that

         A12: X <> {} and

         A13: Y <> {} ;

        for x,y be Real st x in X & y in Y holds x <= y

        proof

          let x,y be Real;

          assume x in X;

          then x in A by XBOOLE_0:def 4;

          then

           A14: ex a st (a = x) & P[a];

          assume y in Y;

          then y in B by XBOOLE_0:def 4;

          then ex a st a = y & Q[a];

          hence thesis by A1, A14;

        end;

        then

        consider s be Real such that

         A15: for x,y be Real st x in X & y in Y holds x <= s & s <= y by AXIOMS: 1;

        reconsider s as ExtReal;

        take s;

        thus for r st P[r] holds r <= s

        proof

          let r;

          consider x be Element of REAL such that

           A16: x in Y by A13;

          x in B by A16, XBOOLE_0:def 4;

          then

           A17: ex a st x = a & Q[a];

          assume

           A18: P[r];

          per cases by A1, A17, A18, XXREAL_0: 13;

            suppose

             A19: r in REAL ;

            then

            reconsider r as Real;

            r is Element of ExtREAL by XXREAL_0:def 1;

            then r in A by A18;

            then r in X by A19, XBOOLE_0:def 4;

            hence thesis by A15, A16;

          end;

            suppose r = -infty ;

            hence thesis by XXREAL_0: 5;

          end;

        end;

        let r;

        consider x be Element of REAL such that

         A20: x in X by A12;

        x in A by A20, XBOOLE_0:def 4;

        then

         A21: ex a st x = a & P[a];

        assume

         A22: Q[r];

        per cases by A1, A21, A22, XXREAL_0: 10;

          suppose

           A23: r in REAL ;

          then

          reconsider r as Real;

          r is Element of ExtREAL by XXREAL_0:def 1;

          then r in B by A22;

          then r in Y by A23, XBOOLE_0:def 4;

          hence thesis by A15, A20;

        end;

          suppose r = +infty ;

          hence thesis by XXREAL_0: 3;

        end;

      end;

    end;

    begin

    definition

      let r,s be ExtReal;

      :: XXREAL_1:def1

      func [.r,s.] -> set equals { a : r <= a & a <= s };

      correctness ;

      :: XXREAL_1:def2

      func [.r,s.[ -> set equals { a : r <= a & a < s };

      correctness ;

      :: XXREAL_1:def3

      func ].r,s.] -> set equals { a : r < a & a <= s };

      correctness ;

      :: XXREAL_1:def4

      func ].r,s.[ -> set equals { a : r < a & a < s };

      correctness ;

    end

    theorem :: XXREAL_1:1

    

     Th1: t in [.r, s.] iff r <= t & t <= s

    proof

      hereby

        assume t in [.r, s.];

        then ex a st a = t & r <= a & a <= s;

        hence r <= t & t <= s;

      end;

      t is Element of ExtREAL by XXREAL_0:def 1;

      hence thesis;

    end;

    theorem :: XXREAL_1:2

    

     Th2: t in ].r, s.] iff r < t & t <= s

    proof

      hereby

        assume t in ].r, s.];

        then ex a st a = t & r < a & a <= s;

        hence r < t & t <= s;

      end;

      t is Element of ExtREAL by XXREAL_0:def 1;

      hence thesis;

    end;

    theorem :: XXREAL_1:3

    

     Th3: t in [.r, s.[ iff r <= t & t < s

    proof

      hereby

        assume t in [.r, s.[;

        then ex a st a = t & r <= a & a < s;

        hence r <= t & t < s;

      end;

      t is Element of ExtREAL by XXREAL_0:def 1;

      hence thesis;

    end;

    theorem :: XXREAL_1:4

    

     Th4: t in ].r, s.[ iff r < t & t < s

    proof

      hereby

        assume t in ].r, s.[;

        then ex a st a = t & r < a & a < s;

        hence r < t & t < s;

      end;

      t is Element of ExtREAL by XXREAL_0:def 1;

      hence thesis;

    end;

    registration

      let r, s;

      cluster [.r, s.] -> ext-real-membered;

      coherence

      proof

        let x be object;

        assume x in [.r, s.];

        then ex a st x = a & r <= a & a <= s;

        hence thesis;

      end;

      cluster [.r, s.[ -> ext-real-membered;

      coherence

      proof

        let x be object;

        assume x in [.r, s.[;

        then ex a st x = a & r <= a & a < s;

        hence thesis;

      end;

      cluster ].r, s.] -> ext-real-membered;

      coherence

      proof

        let x be object;

        assume x in ].r, s.];

        then ex a st x = a & r < a & a <= s;

        hence thesis;

      end;

      cluster ].r, s.[ -> ext-real-membered;

      coherence

      proof

        let x be object;

        assume x in ].r, s.[;

        then ex a st x = a & r < a & a < s;

        hence thesis;

      end;

    end

    theorem :: XXREAL_1:5

    

     Th5: x in [.p, q.] implies x in ].p, q.[ or x = p or x = q

    proof

      assume

       A1: x in [.p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th1;

      

       A3: s <= q by A1, Th1;

      

       A4: p = s or p < s by A2, XXREAL_0: 1;

      s = q or s < q by A3, XXREAL_0: 1;

      hence thesis by A4, Th4;

    end;

    theorem :: XXREAL_1:6

    

     Th6: x in [.p, q.] implies x in ].p, q.] or x = p

    proof

      assume

       A1: x in [.p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th1;

      

       A3: s <= q by A1, Th1;

      p = s or p < s by A2, XXREAL_0: 1;

      hence thesis by A3, Th2;

    end;

    theorem :: XXREAL_1:7

    

     Th7: x in [.p, q.] implies x in [.p, q.[ or x = q

    proof

      assume

       A1: x in [.p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th1;

      s <= q by A1, Th1;

      then q = s or s < q by XXREAL_0: 1;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:8

    

     Th8: x in [.p, q.[ implies x in ].p, q.[ or x = p

    proof

      assume

       A1: x in [.p, q.[;

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th3;

      

       A3: s < q by A1, Th3;

      p = s or p < s by A2, XXREAL_0: 1;

      hence thesis by A3, Th4;

    end;

    theorem :: XXREAL_1:9

    

     Th9: x in ].p, q.] implies x in ].p, q.[ or x = q

    proof

      assume

       A1: x in ].p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p < s by A1, Th2;

      s <= q by A1, Th2;

      then q = s or s < q by XXREAL_0: 1;

      hence thesis by A2, Th4;

    end;

    theorem :: XXREAL_1:10

    x in [.p, q.[ implies x in ].p, q.] & x <> q or x = p

    proof

      assume

       A1: x in [.p, q.[;

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th3;

      

       A3: s < q by A1, Th3;

      p = s or p < s by A2, XXREAL_0: 1;

      hence thesis by A3, Th2;

    end;

    theorem :: XXREAL_1:11

    x in ].p, q.] implies x in [.p, q.[ & x <> p or x = q

    proof

      assume

       A1: x in ].p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p < s by A1, Th2;

      s <= q by A1, Th2;

      then q = s or s < q by XXREAL_0: 1;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:12

    

     Th12: x in ].p, q.] implies x in [.p, q.] & x <> p

    proof

      assume

       A1: x in ].p, q.];

      then

      reconsider s = x as ExtReal;

      

       A2: p < s by A1, Th2;

      s <= q by A1, Th2;

      hence thesis by A2, Th1;

    end;

    theorem :: XXREAL_1:13

    

     Th13: x in [.p, q.[ implies x in [.p, q.] & x <> q

    proof

      assume

       A1: x in [.p, q.[;

      then

      reconsider s = x as ExtReal;

      

       A2: p <= s by A1, Th3;

      s < q by A1, Th3;

      hence thesis by A2, Th1;

    end;

    theorem :: XXREAL_1:14

    

     Th14: x in ].p, q.[ implies x in [.p, q.[ & x <> p

    proof

      assume

       A1: x in ].p, q.[;

      then

      reconsider s = x as ExtReal;

      

       A2: p < s by A1, Th4;

      s < q by A1, Th4;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:15

    

     Th15: x in ].p, q.[ implies x in ].p, q.] & x <> q

    proof

      assume

       A1: x in ].p, q.[;

      then

      reconsider s = x as ExtReal;

      

       A2: p < s by A1, Th4;

      s < q by A1, Th4;

      hence thesis by A2, Th2;

    end;

    theorem :: XXREAL_1:16

    

     Th16: x in ].p, q.[ implies x in [.p, q.] & x <> p & x <> q

    proof

      assume

       A1: x in ].p, q.[;

      then x in ].p, q.] by Th15;

      hence thesis by A1, Th12, Th15;

    end;

    theorem :: XXREAL_1:17

    

     Th17: [.r, r.] = {r}

    proof

      let s;

      thus s in [.r, r.] implies s in {r}

      proof

        assume s in [.r, r.];

        then ex a st s = a & r <= a & a <= r;

        then s = r by XXREAL_0: 1;

        hence thesis by TARSKI:def 1;

      end;

      assume s in {r};

      then

       A1: s = r by TARSKI:def 1;

      reconsider s as Element of ExtREAL by XXREAL_0:def 1;

      s <= s;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:18

    

     Th18: [.r, r.[ = {}

    proof

      let p;

       not ex p st p in [.r, r.[

      proof

        given p such that

         A1: p in [.r, r.[;

        ex a st p = a & r <= a & a < r by A1;

        hence thesis;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:19

    

     Th19: ].r, r.] = {}

    proof

      let p;

      thus p in ].r, r.] implies p in {}

      proof

        assume p in ].r, r.];

        then ex a st p = a & r < a & a <= r;

        hence thesis;

      end;

      thus thesis;

    end;

    theorem :: XXREAL_1:20

    

     Th20: ].r, r.[ = {}

    proof

      let p;

      thus p in ].r, r.[ implies p in {}

      proof

        assume p in ].r, r.[;

        then ex a st p = a & r < a & a < r;

        hence thesis;

      end;

      thus thesis;

    end;

    registration

      let r;

      cluster [.r, r.] -> non empty;

      coherence

      proof

         [.r, r.] = {r} by Th17;

        hence thesis;

      end;

      cluster [.r, r.[ -> empty;

      coherence by Th18;

      cluster ].r, r.] -> empty;

      coherence by Th19;

      cluster ].r, r.[ -> empty;

      coherence by Th20;

    end

    theorem :: XXREAL_1:21

    

     Th21: ].p, q.[ c= ].p, q.]

    proof

      let s;

      assume

       A1: s in ].p, q.[;

      then

       A2: p < s by Th4;

      s < q by A1, Th4;

      hence thesis by A2, Th2;

    end;

    theorem :: XXREAL_1:22

    

     Th22: ].p, q.[ c= [.p, q.[

    proof

      let s;

      assume

       A1: s in ].p, q.[;

      then

       A2: p < s by Th4;

      s < q by A1, Th4;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:23

    

     Th23: ].p, q.] c= [.p, q.]

    proof

      let s;

      assume

       A1: s in ].p, q.];

      then

       A2: p < s by Th2;

      s <= q by A1, Th2;

      hence thesis by A2, Th1;

    end;

    theorem :: XXREAL_1:24

    

     Th24: [.p, q.[ c= [.p, q.]

    proof

      let s;

      assume

       A1: s in [.p, q.[;

      then

       A2: p <= s by Th3;

      s < q by A1, Th3;

      hence thesis by A2, Th1;

    end;

    theorem :: XXREAL_1:25

    

     Th25: ].p, q.[ c= [.p, q.]

    proof

      

       A1: ].p, q.[ c= [.p, q.[ by Th22;

       [.p, q.[ c= [.p, q.] by Th24;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:26

    p <= q implies ].q, p.] = {}

    proof

      assume

       A1: p <= q;

      assume ].q, p.] <> {} ;

      then

      consider r such that

       A2: r in ].q, p.];

      

       A3: q < r by A2, Th2;

      r <= p by A2, Th2;

      hence contradiction by A1, A3, XXREAL_0: 2;

    end;

    theorem :: XXREAL_1:27

    

     Th27: p <= q implies [.q, p.[ = {}

    proof

      assume

       A1: p <= q;

      assume [.q, p.[ <> {} ;

      then

      consider r such that

       A2: r in [.q, p.[;

      

       A3: q <= r by A2, Th3;

      r < p by A2, Th3;

      hence contradiction by A1, A3, XXREAL_0: 2;

    end;

    theorem :: XXREAL_1:28

    

     Th28: p <= q implies ].q, p.[ = {}

    proof

      assume p <= q;

      then [.q, p.[ = {} by Th27;

      hence thesis by Th22, XBOOLE_1: 3;

    end;

    theorem :: XXREAL_1:29

    

     Th29: p < q implies [.q, p.] = {}

    proof

      assume

       A1: p < q;

      assume [.q, p.] <> {} ;

      then

      consider r such that

       A2: r in [.q, p.];

      

       A3: q <= r by A2, Th1;

      r <= p by A2, Th1;

      hence contradiction by A1, A3, XXREAL_0: 2;

    end;

    theorem :: XXREAL_1:30

    r <= s implies [.r, s.] is non empty by Th1;

    theorem :: XXREAL_1:31

    p < q implies [.p, q.[ is non empty by Th3;

    theorem :: XXREAL_1:32

    p < q implies ].p, q.] is non empty by Th2;

    theorem :: XXREAL_1:33

    p < q implies ].p, q.[ is non empty

    proof

      assume p < q;

      then ex s st p < s & s < q by XREAL_1: 227;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:34

    

     Th34: p <= r & s <= q implies [.r, s.] c= [.p, q.]

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in [.r, s.];

      then

       A4: r <= t by Th1;

      

       A5: t <= s by A3, Th1;

      

       A6: p <= t by A1, A4, XXREAL_0: 2;

      t <= q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th1;

    end;

    theorem :: XXREAL_1:35

    

     Th35: p <= r & s <= q implies [.r, s.[ c= [.p, q.]

    proof

      

       A1: [.r, s.[ c= [.r, s.] by Th24;

      assume that

       A2: p <= r and

       A3: s <= q;

       [.r, s.] c= [.p, q.] by A2, A3, Th34;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:36

    

     Th36: p <= r & s <= q implies ].r, s.] c= [.p, q.]

    proof

      

       A1: ].r, s.] c= [.r, s.] by Th23;

      assume that

       A2: p <= r and

       A3: s <= q;

       [.r, s.] c= [.p, q.] by A2, A3, Th34;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:37

    

     Th37: p <= r & s <= q implies ].r, s.[ c= [.p, q.]

    proof

      

       A1: ].r, s.[ c= [.r, s.] by Th25;

      assume that

       A2: p <= r and

       A3: s <= q;

       [.r, s.] c= [.p, q.] by A2, A3, Th34;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:38

    

     Th38: p <= r & s <= q implies [.r, s.[ c= [.p, q.[

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in [.r, s.[;

      then

       A4: r <= t by Th3;

      

       A5: t < s by A3, Th3;

      

       A6: p <= t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th3;

    end;

    theorem :: XXREAL_1:39

    

     Th39: p < r & s <= q implies [.r, s.] c= ].p, q.]

    proof

      assume that

       A1: p < r and

       A2: s <= q;

      let t;

      assume

       A3: t in [.r, s.];

      then

       A4: r <= t by Th1;

      

       A5: t <= s by A3, Th1;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t <= q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th2;

    end;

    theorem :: XXREAL_1:40

    

     Th40: p < r & s <= q implies [.r, s.[ c= ].p, q.]

    proof

      

       A1: [.r, s.[ c= [.r, s.] by Th24;

      assume that

       A2: p < r and

       A3: s <= q;

       [.r, s.] c= ].p, q.] by A2, A3, Th39;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:41

    

     Th41: p <= r & s <= q implies ].r, s.[ c= ].p, q.]

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in ].r, s.[;

      then

       A4: r < t by Th4;

      

       A5: t < s by A3, Th4;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th2;

    end;

    theorem :: XXREAL_1:42

    

     Th42: p <= r & s <= q implies ].r, s.] c= ].p, q.]

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in ].r, s.];

      then

       A4: r < t by Th2;

      

       A5: t <= s by A3, Th2;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t <= q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th2;

    end;

    theorem :: XXREAL_1:43

    

     Th43: p <= r & s < q implies [.r, s.] c= [.p, q.[

    proof

      assume that

       A1: p <= r and

       A2: s < q;

      let t;

      assume

       A3: t in [.r, s.];

      then

       A4: r <= t by Th1;

      

       A5: t <= s by A3, Th1;

      

       A6: p <= t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th3;

    end;

    theorem :: XXREAL_1:44

    

     Th44: p <= r & s < q implies ].r, s.] c= [.p, q.[

    proof

      

       A1: ].r, s.] c= [.r, s.] by Th23;

      assume that

       A2: p <= r and

       A3: s < q;

       [.r, s.] c= [.p, q.[ by A2, A3, Th43;

      hence thesis by A1;

    end;

    theorem :: XXREAL_1:45

    

     Th45: p <= r & s <= q implies ].r, s.[ c= [.p, q.[

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in ].r, s.[;

      then

       A4: r < t by Th4;

      

       A5: t < s by A3, Th4;

      

       A6: p <= t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th3;

    end;

    theorem :: XXREAL_1:46

    

     Th46: p <= r & s <= q implies ].r, s.[ c= ].p, q.[

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      let t;

      assume

       A3: t in ].r, s.[;

      then

       A4: r < t by Th4;

      

       A5: t < s by A3, Th4;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th4;

    end;

    theorem :: XXREAL_1:47

    

     Th47: p < r & s < q implies [.r, s.] c= ].p, q.[

    proof

      assume that

       A1: p < r and

       A2: s < q;

      let t;

      assume

       A3: t in [.r, s.];

      then

       A4: r <= t by Th1;

      

       A5: t <= s by A3, Th1;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th4;

    end;

    theorem :: XXREAL_1:48

    

     Th48: p < r & s <= q implies [.r, s.[ c= ].p, q.[

    proof

      assume that

       A1: p < r and

       A2: s <= q;

      let t;

      assume

       A3: t in [.r, s.[;

      then

       A4: r <= t by Th3;

      

       A5: t < s by A3, Th3;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th4;

    end;

    theorem :: XXREAL_1:49

    

     Th49: p <= r & s < q implies ].r, s.] c= ].p, q.[

    proof

      assume that

       A1: p <= r and

       A2: s < q;

      let t;

      assume

       A3: t in ].r, s.];

      then

       A4: r < t by Th2;

      

       A5: t <= s by A3, Th2;

      

       A6: p < t by A1, A4, XXREAL_0: 2;

      t < q by A2, A5, XXREAL_0: 2;

      hence thesis by A6, Th4;

    end;

    theorem :: XXREAL_1:50

    

     Th50: r <= s & [.r, s.] c= [.p, q.] implies p <= r & s <= q

    proof

      assume

       A1: r <= s;

      then

       A2: r in [.r, s.] by Th1;

      s in [.r, s.] by A1, Th1;

      hence thesis by A2, Th1;

    end;

    theorem :: XXREAL_1:51

    

     Th51: r < s & ].r, s.[ c= [.p, q.] implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ c= [.p, q.];

      now

        let t;

        assume that

         A3: r < t and

         A4: t < s;

        t in ].r, s.[ by A3, A4, Th4;

        hence p <= t by A2, Th1;

      end;

      hence p <= r by A1, XREAL_1: 228;

      now

        let t;

        assume that

         A5: r < t and

         A6: t < s;

        t in ].r, s.[ by A5, A6, Th4;

        hence t <= q by A2, Th1;

      end;

      hence thesis by A1, XREAL_1: 229;

    end;

    theorem :: XXREAL_1:52

    

     Th52: r < s & [.r, s.[ c= [.p, q.] implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ c= [.p, q.];

       ].r, s.[ c= [.r, s.[ by Th22;

      then ].r, s.[ c= [.p, q.] by A2;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:53

    

     Th53: r < s & ].r, s.] c= [.p, q.] implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] c= [.p, q.];

       ].r, s.[ c= ].r, s.] by Th21;

      then ].r, s.[ c= [.p, q.] by A2;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:54

    

     Th54: r <= s & [.r, s.] c= [.p, q.[ implies p <= r & s < q

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] c= [.p, q.[;

       [.p, q.[ c= [.p, q.] by Th24;

      then [.r, s.] c= [.p, q.] by A2;

      hence p <= r by A1, Th50;

      s in [.r, s.] by A1, Th1;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:55

    

     Th55: r < s & [.r, s.[ c= [.p, q.[ implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ c= [.p, q.[;

       ].r, s.[ c= [.r, s.[ by Th22;

      then

       A3: ].r, s.[ c= [.p, q.[ by A2;

       [.p, q.[ c= [.p, q.] by Th24;

      then ].r, s.[ c= [.p, q.] by A3;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:56

    

     Th56: r < s & ].r, s.[ c= [.p, q.[ implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ c= [.p, q.[;

       [.p, q.[ c= [.p, q.] by Th24;

      then ].r, s.[ c= [.p, q.] by A2;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:57

    

     Th57: r < s & ].r, s.] c= [.p, q.[ implies p <= r & s < q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] c= [.p, q.[;

       [.p, q.[ c= [.p, q.] by Th24;

      then ].r, s.] c= [.p, q.] by A2;

      hence p <= r by A1, Th53;

      s in ].r, s.] by A1, Th2;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:58

    

     Th58: r <= s & [.r, s.] c= ].p, q.] implies p < r & s <= q

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] c= ].p, q.];

       ].p, q.] c= [.p, q.] by Th23;

      then

       A3: [.r, s.] c= [.p, q.] by A2;

      r in [.r, s.] by A1, Th1;

      hence p < r by A2, Th2;

      thus thesis by A1, A3, Th50;

    end;

    theorem :: XXREAL_1:59

    

     Th59: r < s & ].r, s.[ c= ].p, q.] implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ c= ].p, q.];

       ].p, q.] c= [.p, q.] by Th23;

      then ].r, s.[ c= [.p, q.] by A2;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:60

    

     Th60: r < s & [.r, s.[ c= ].p, q.] implies p < r & s <= q

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ c= ].p, q.];

       ].p, q.] c= [.p, q.] by Th23;

      then

       A3: [.r, s.[ c= [.p, q.] by A2;

      r in [.r, s.[ by A1, Th3;

      hence p < r by A2, Th2;

      thus thesis by A1, A3, Th52;

    end;

    theorem :: XXREAL_1:61

    

     Th61: r < s & ].r, s.] c= ].p, q.] implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] c= ].p, q.];

       ].r, s.[ c= ].r, s.] by Th21;

      then

       A3: ].r, s.[ c= ].p, q.] by A2;

       ].p, q.] c= [.p, q.] by Th23;

      then ].r, s.[ c= [.p, q.] by A3;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:62

    

     Th62: r <= s & [.r, s.] c= ].p, q.[ implies p < r & s < q

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] c= ].p, q.[;

      r in [.r, s.] by A1, Th1;

      hence p < r by A2, Th4;

      s in [.r, s.] by A1, Th1;

      hence thesis by A2, Th4;

    end;

    theorem :: XXREAL_1:63

    

     Th63: r < s & ].r, s.[ c= ].p, q.[ implies p <= r & s <= q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ c= ].p, q.[;

       ].p, q.[ c= [.p, q.] by Th25;

      then ].r, s.[ c= [.p, q.] by A2;

      hence thesis by A1, Th51;

    end;

    theorem :: XXREAL_1:64

    

     Th64: r < s & [.r, s.[ c= ].p, q.[ implies p < r & s <= q

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ c= ].p, q.[;

       ].p, q.[ c= [.p, q.] by Th25;

      then

       A3: [.r, s.[ c= [.p, q.] by A2;

      r in [.r, s.[ by A1, Th3;

      hence p < r by A2, Th4;

      thus thesis by A1, A3, Th52;

    end;

    theorem :: XXREAL_1:65

    

     Th65: r < s & ].r, s.] c= ].p, q.[ implies p <= r & s < q

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] c= ].p, q.[;

       ].p, q.[ c= [.p, q.] by Th25;

      then ].r, s.] c= [.p, q.] by A2;

      hence p <= r by A1, Th53;

      s in ].r, s.] by A1, Th2;

      hence thesis by A2, Th4;

    end;

    theorem :: XXREAL_1:66

    p <= q & [.p, q.] = [.r, s.] implies p = r & q = s

    proof

      assume that

       A1: p <= q and

       A2: [.p, q.] = [.r, s.];

      

       A3: r <= p by A1, A2, Th50;

      

       A4: q <= s by A1, A2, Th50;

      r <= q by A1, A3, XXREAL_0: 2;

      then

       A5: r <= s by A4, XXREAL_0: 2;

      then

       A6: p <= r by A2, Th50;

      s <= q by A2, A5, Th50;

      hence thesis by A3, A4, A6, XXREAL_0: 1;

    end;

    theorem :: XXREAL_1:67

    p < q & ].p, q.[ = ].r, s.[ implies p = r & q = s

    proof

      assume that

       A1: p < q and

       A2: ].p, q.[ = ].r, s.[;

      

       A3: r <= p by A1, A2, Th63;

      

       A4: q <= s by A1, A2, Th63;

      r < q by A1, A3, XXREAL_0: 2;

      then

       A5: r < s by A4, XXREAL_0: 2;

      then

       A6: p <= r by A2, Th63;

      s <= q by A2, A5, Th63;

      hence thesis by A3, A4, A6, XXREAL_0: 1;

    end;

    theorem :: XXREAL_1:68

    p < q & ].p, q.] = ].r, s.] implies p = r & q = s

    proof

      assume that

       A1: p < q and

       A2: ].p, q.] = ].r, s.];

      

       A3: r <= p by A1, A2, Th61;

      

       A4: q <= s by A1, A2, Th61;

      r < q by A1, A3, XXREAL_0: 2;

      then

       A5: r < s by A4, XXREAL_0: 2;

      then

       A6: p <= r by A2, Th61;

      s <= q by A2, A5, Th61;

      hence thesis by A3, A4, A6, XXREAL_0: 1;

    end;

    theorem :: XXREAL_1:69

    p < q & [.p, q.[ = [.r, s.[ implies p = r & q = s

    proof

      assume that

       A1: p < q and

       A2: [.p, q.[ = [.r, s.[;

      

       A3: r <= p by A1, A2, Th55;

      

       A4: q <= s by A1, A2, Th55;

      r < q by A1, A3, XXREAL_0: 2;

      then

       A5: r < s by A4, XXREAL_0: 2;

      then

       A6: p <= r by A2, Th55;

      s <= q by A2, A5, Th55;

      hence thesis by A3, A4, A6, XXREAL_0: 1;

    end;

    theorem :: XXREAL_1:70

    r <= s implies [.r, s.] <> ].p, q.]

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] = ].p, q.];

      now

        assume r in ].p, q.];

        then

         A3: p < r by Th2;

        s <= q by A1, A2, Th58;

        then r <= q by A1, XXREAL_0: 2;

        then p < q by A3, XXREAL_0: 2;

        hence contradiction by A2, A3, Th53;

      end;

      hence contradiction by A1, A2, Th1;

    end;

    theorem :: XXREAL_1:71

    r <= s implies [.r, s.] <> [.p, q.[

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] = [.p, q.[;

      now

        assume s in [.p, q.[;

        then

         A3: s < q by Th3;

        p <= r by A1, A2, Th54;

        then p <= s by A1, XXREAL_0: 2;

        then p < q by A3, XXREAL_0: 2;

        hence contradiction by A2, A3, Th52;

      end;

      hence contradiction by A1, A2, Th1;

    end;

    theorem :: XXREAL_1:72

    r <= s implies [.r, s.] <> ].p, q.[

    proof

      assume that

       A1: r <= s and

       A2: [.r, s.] = ].p, q.[;

      now

        assume s in ].p, q.[;

        then

         A3: s < q by Th4;

        p <= r by A1, A2, Th62;

        then p <= s by A1, XXREAL_0: 2;

        then p < q by A3, XXREAL_0: 2;

        hence contradiction by A2, A3, Th51;

      end;

      hence contradiction by A1, A2, Th1;

    end;

    theorem :: XXREAL_1:73

    r < s implies [.r, s.[ <> [.p, q.]

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ = [.p, q.];

      

       A3: not s in [.r, s.[ by Th3;

      p <= r by A1, A2, Th52;

      then

       A4: p <= s by A1, XXREAL_0: 2;

      s <= q by A1, A2, Th52;

      hence contradiction by A2, A3, A4, Th1;

    end;

    theorem :: XXREAL_1:74

    r < s implies [.r, s.[ <> ].p, q.]

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ = ].p, q.];

      

       A3: not s in [.r, s.[ by Th3;

      p <= r by A1, A2, Th60;

      then

       A4: p < s by A1, XXREAL_0: 2;

      s <= q by A1, A2, Th60;

      hence contradiction by A2, A3, A4, Th2;

    end;

    theorem :: XXREAL_1:75

    r < s implies [.r, s.[ <> ].p, q.[

    proof

      assume that

       A1: r < s and

       A2: [.r, s.[ = ].p, q.[;

      now

        assume r in ].p, q.[;

        then

         A3: p < r by Th4;

        s <= q by A1, A2, Th64;

        then r < q by A1, XXREAL_0: 2;

        then p < q by A3, XXREAL_0: 2;

        hence contradiction by A2, A3, Th56;

      end;

      hence contradiction by A1, A2, Th3;

    end;

    theorem :: XXREAL_1:76

    r < s implies ].r, s.] <> [.p, q.]

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] = [.p, q.];

      

       A3: not r in ].r, s.] by Th2;

      

       A4: p <= r by A1, A2, Th53;

      s <= q by A1, A2, Th53;

      then r <= q by A1, XXREAL_0: 2;

      hence contradiction by A2, A3, A4, Th1;

    end;

    theorem :: XXREAL_1:77

    r < s implies ].r, s.] <> [.p, q.[

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] = [.p, q.[;

      

       A3: not r in ].r, s.] by Th2;

      

       A4: p <= r by A1, A2, Th57;

      s <= q by A1, A2, Th57;

      then r < q by A1, XXREAL_0: 2;

      hence contradiction by A2, A3, A4, Th3;

    end;

    theorem :: XXREAL_1:78

    r < s implies ].r, s.] <> ].p, q.[

    proof

      assume that

       A1: r < s and

       A2: ].r, s.] = ].p, q.[;

      now

        assume s in ].p, q.[;

        then

         A3: s < q by Th4;

        p <= r by A1, A2, Th65;

        then p <= s by A1, XXREAL_0: 2;

        then p < q by A3, XXREAL_0: 2;

        hence contradiction by A2, A3, Th59;

      end;

      hence contradiction by A1, A2, Th2;

    end;

    theorem :: XXREAL_1:79

    r < s implies ].r, s.[ <> [.p, q.]

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ = [.p, q.];

      

       A3: not r in ].r, s.[ by Th4;

      

       A4: p <= r by A1, A2, Th51;

      s <= q by A1, A2, Th51;

      then r <= q by A1, XXREAL_0: 2;

      hence contradiction by A2, A3, A4, Th1;

    end;

    theorem :: XXREAL_1:80

    r < s implies ].r, s.[ <> ].p, q.]

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ = ].p, q.];

      

       A3: not s in ].r, s.[ by Th4;

      p <= r by A1, A2, Th59;

      then

       A4: p < s by A1, XXREAL_0: 2;

      s <= q by A1, A2, Th59;

      hence contradiction by A2, A3, A4, Th2;

    end;

    theorem :: XXREAL_1:81

    r < s implies ].r, s.[ <> [.p, q.[

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ = [.p, q.[;

      

       A3: not r in ].r, s.[ by Th4;

      

       A4: p <= r by A1, A2, Th56;

      s <= q by A1, A2, Th56;

      then r < q by A1, XXREAL_0: 2;

      hence contradiction by A2, A3, A4, Th3;

    end;

    theorem :: XXREAL_1:82

    r <= s & [.r, s.] c< [.p, q.] implies p < r or s < q

    proof

      assume

       A1: r <= s;

      assume

       A2: [.r, s.] c< [.p, q.];

      then

       A3: [.r, s.] c= [.p, q.];

      then

       A4: p <= r by A1, Th50;

      

       A5: s <= q by A1, A3, Th50;

      p <> r or s <> q by A2;

      hence thesis by A4, A5, XXREAL_0: 1;

    end;

    theorem :: XXREAL_1:83

    r < s & ].r, s.[ c= [.p, q.] implies [.r, s.] c= [.p, q.]

    proof

      assume that

       A1: r < s and

       A2: ].r, s.[ c= [.p, q.];

      let t;

      assume

       A3: t in [.r, s.];

      per cases by A3, Th5;

        suppose t in ].r, s.[;

        hence thesis by A2;

      end;

        suppose

         A4: t = r;

        then

         A5: p <= t by A1, A2, Th51;

        s <= q by A1, A2, Th51;

        then t <= q by A1, A4, XXREAL_0: 2;

        hence thesis by A5, Th1;

      end;

        suppose

         A6: t = s;

        

         A7: s <= q by A1, A2, Th51;

        p <= r by A1, A2, Th51;

        then p <= t by A1, A6, XXREAL_0: 2;

        hence thesis by A6, A7, Th1;

      end;

    end;

    theorem :: XXREAL_1:84

    r < s implies [.s, p.[ c= ].r, p.[

    proof

      assume

       A1: r < s;

      let t;

      assume

       A2: t in [.s, p.[;

      then s <= t by Th3;

      then

       A3: r < t by A1, XXREAL_0: 2;

      t < p by A2, Th3;

      hence thesis by A3, Th4;

    end;

    theorem :: XXREAL_1:85

    

     Th85: s <= r implies [.r, s.] c= {r} & [.r, s.] c= {s}

    proof

      assume

       A1: s <= r;

      thus [.r, s.] c= {r}

      proof

        let t;

        assume

         A2: t in [.r, s.];

        then

         A3: t <= s by Th1;

        

         A4: r <= t by A2, Th1;

        t <= r by A1, A3, XXREAL_0: 2;

        then r = t by A4, XXREAL_0: 1;

        hence thesis by TARSKI:def 1;

      end;

      let t;

      assume

       A5: t in [.r, s.];

      then r <= t by Th1;

      then

       A6: s <= t by A1, XXREAL_0: 2;

      t <= s by A5, Th1;

      then s = t by A6, XXREAL_0: 1;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:86

     ].r, s.[ misses {r, s}

    proof

      let t;

      assume

       A1: t in ].r, s.[;

      then

       A2: r < t by Th4;

      t < s by A1, Th4;

      hence thesis by A2, TARSKI:def 2;

    end;

    theorem :: XXREAL_1:87

     [.r, s.[ misses {s}

    proof

      let t;

      assume t in [.r, s.[;

      then t < s by Th3;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:88

     ].r, s.] misses {r}

    proof

      let t;

      assume t in ].r, s.];

      then r < t by Th2;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:89

    s <= p implies [.r, s.] misses ].p, q.[

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.];

      then t <= s by Th1;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:90

    s <= p implies [.r, s.] misses ].p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.];

      then t <= s by Th1;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th2;

    end;

    theorem :: XXREAL_1:91

    s <= p implies ].r, s.] misses ].p, q.[

    proof

      assume

       A1: s <= p;

      let t;

      assume t in ].r, s.];

      then t <= s by Th2;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:92

    s <= p implies ].r, s.] misses ].p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in ].r, s.];

      then t <= s by Th2;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th2;

    end;

    theorem :: XXREAL_1:93

    s <= p implies ].r, s.[ misses [.p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in ].r, s.[;

      then t < s by Th4;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:94

    s <= p implies ].r, s.[ misses [.p, q.[

    proof

      assume

       A1: s <= p;

      let t;

      assume t in ].r, s.[;

      then t < s by Th4;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th3;

    end;

    theorem :: XXREAL_1:95

    s <= p implies [.r, s.[ misses [.p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.[;

      then t < s by Th3;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:96

    s <= p implies [.r, s.[ misses [.p, q.[

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.[;

      then t < s by Th3;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th3;

    end;

    theorem :: XXREAL_1:97

    r < p & r < s implies not ].r, s.[ c= [.p, q.]

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A4, A5, Th4;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th1;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.[ by A7, Th4;

        thus thesis by A8, Th1;

      end;

    end;

    theorem :: XXREAL_1:98

    r < p & r < s implies not [.r, s.[ c= [.p, q.]

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A4, A5, Th3;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th1;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in [.r, s.[ by A7, Th3;

        thus thesis by A8, Th1;

      end;

    end;

    theorem :: XXREAL_1:99

    r < p & r < s implies not ].r, s.] c= [.p, q.]

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A4, A5, Th2;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th1;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.] by A7, Th2;

        thus thesis by A8, Th1;

      end;

    end;

    theorem :: XXREAL_1:100

    r < p & r <= s implies not [.r, s.] c= [.p, q.]

    proof

      assume that

       A1: r < p and

       A2: r <= s;

      take t = r;

      thus t in [.r, s.] by A2, Th1;

      thus thesis by A1, Th1;

    end;

    theorem :: XXREAL_1:101

    r < p & r < s implies not ].r, s.[ c= [.p, q.[

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A4, A5, Th4;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th3;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.[ by A7, Th4;

        thus thesis by A8, Th3;

      end;

    end;

    theorem :: XXREAL_1:102

    r < p & r < s implies not ].r, s.] c= [.p, q.[

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A4, A5, Th2;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th3;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.] by A7, Th2;

        thus thesis by A8, Th3;

      end;

    end;

    theorem :: XXREAL_1:103

    r < p & r < s implies not [.r, s.[ c= [.p, q.[

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A4, A5, Th3;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th3;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in [.r, s.[ by A7, Th3;

        thus thesis by A8, Th3;

      end;

    end;

    theorem :: XXREAL_1:104

    r < p & r <= s implies not [.r, s.] c= [.p, q.[

    proof

      assume that

       A1: r < p and

       A2: r <= s;

      take t = r;

      thus t in [.r, s.] by A2, Th1;

      thus thesis by A1, Th3;

    end;

    theorem :: XXREAL_1:105

    r < p & r < s implies not ].r, s.[ c= ].p, q.]

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A4, A5, Th4;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th2;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.[ by A7, Th4;

        thus thesis by A8, Th2;

      end;

    end;

    theorem :: XXREAL_1:106

    r <= p & r < s implies not [.r, s.[ c= ].p, q.]

    proof

      assume that

       A1: r <= p and

       A2: r < s;

      take t = r;

      thus t in [.r, s.[ by A2, Th3;

      thus thesis by A1, Th2;

    end;

    theorem :: XXREAL_1:107

    r < p & r < s implies not ].r, s.] c= ].p, q.]

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A4, A5, Th2;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th2;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t <= s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.] by A7, Th2;

        thus thesis by A8, Th2;

      end;

    end;

    theorem :: XXREAL_1:108

    r <= p & r <= s implies not [.r, s.] c= ].p, q.]

    proof

      assume that

       A1: r <= p and

       A2: r <= s;

      take r;

      thus r in [.r, s.] by A2, Th1;

      thus thesis by A1, Th2;

    end;

    theorem :: XXREAL_1:109

    r <= p & r <= s implies not [.r, s.] c= ].p, q.[

    proof

      assume that

       A1: r <= p and

       A2: r <= s;

      take r;

      thus r in [.r, s.] by A2, Th1;

      thus thesis by A1, Th4;

    end;

    theorem :: XXREAL_1:110

    r <= p & r < s implies not [.r, s.[ c= ].p, q.[

    proof

      assume that

       A1: r <= p and

       A2: r < s;

      take r;

      thus r in [.r, s.[ by A2, Th3;

      thus thesis by A1, Th4;

    end;

    theorem :: XXREAL_1:111

    r < p & r < s implies not ].r, s.] c= ].p, q.[

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A4, A5, Th2;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th4;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t <= s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.] by A7, Th2;

        thus thesis by A8, Th4;

      end;

    end;

    theorem :: XXREAL_1:112

    r < p & r < s implies not ].r, s.[ c= ].p, q.[

    proof

      assume that

       A1: r < p and

       A2: r < s;

      per cases ;

        suppose

         A3: s <= p;

        consider t such that

         A4: r < t and

         A5: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A4, A5, Th4;

        t < p by A3, A5, XXREAL_0: 2;

        hence thesis by Th4;

      end;

        suppose

         A6: p <= s;

        consider t such that

         A7: r < t and

         A8: t < p by A1, XREAL_1: 227;

        take t;

        t < s by A6, A8, XXREAL_0: 2;

        hence t in ].r, s.[ by A7, Th4;

        thus thesis by A8, Th4;

      end;

    end;

    theorem :: XXREAL_1:113

    q < s & r < s implies not ].r, s.[ c= [.p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.[ by A5, Th4;

        thus thesis by A4, Th1;

      end;

        suppose

         A6: q <= r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A7, A8, Th4;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th1;

      end;

    end;

    theorem :: XXREAL_1:114

    q < s & r < s implies not [.r, s.[ c= [.p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in [.r, s.[ by A5, Th3;

        thus thesis by A4, Th1;

      end;

        suppose

         A6: q <= r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A7, A8, Th3;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th1;

      end;

    end;

    theorem :: XXREAL_1:115

    q < s & r < s implies not ].r, s.] c= [.p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.] by A5, Th2;

        thus thesis by A4, Th1;

      end;

        suppose

         A6: q <= r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A7, A8, Th2;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th1;

      end;

    end;

    theorem :: XXREAL_1:116

    q < s & r <= s implies not [.r, s.] c= [.p, q.]

    proof

      assume that

       A1: q < s and

       A2: r <= s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in [.r, s.] by A5, Th1;

        thus thesis by A4, Th1;

      end;

        suppose

         A6: q < r;

        take t = r;

        thus t in [.r, s.] by A2, Th1;

        thus thesis by A6, Th1;

      end;

    end;

    theorem :: XXREAL_1:117

    q < s & r < s implies not ].r, s.[ c= [.p, q.[

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.[ by A5, Th4;

        thus thesis by A4, Th3;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A7, A8, Th4;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th3;

      end;

    end;

    theorem :: XXREAL_1:118

    q <= s & r < s implies not ].r, s.] c= [.p, q.[

    proof

      assume that

       A1: q <= s and

       A2: r < s;

      take t = s;

      thus t in ].r, s.] by A2, Th2;

      thus thesis by A1, Th3;

    end;

    theorem :: XXREAL_1:119

    q < s & r < s implies not [.r, s.[ c= [.p, q.[

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in [.r, s.[ by A5, Th3;

        thus thesis by A4, Th3;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A7, A8, Th3;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th3;

      end;

    end;

    theorem :: XXREAL_1:120

    q < s & r < s implies not ].r, s.[ c= ].p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.[ by A5, Th4;

        thus thesis by A4, Th2;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A7, A8, Th4;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th2;

      end;

    end;

    theorem :: XXREAL_1:121

    q < s & r <= s implies not [.r, s.] c= ].p, q.]

    proof

      assume that

       A1: q < s and

       A2: r <= s;

      take t = s;

      thus t in [.r, s.] by A2, Th1;

      thus thesis by A1, Th2;

    end;

    theorem :: XXREAL_1:122

    q < s & r < s implies not [.r, s.[ c= ].p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in [.r, s.[ by A5, Th3;

        thus thesis by A4, Th2;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A7, A8, Th3;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th2;

      end;

    end;

    theorem :: XXREAL_1:123

    q < s & r < s implies not ].r, s.] c= ].p, q.]

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.] by A5, Th2;

        thus thesis by A4, Th2;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.] by A7, A8, Th2;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th2;

      end;

    end;

    theorem :: XXREAL_1:124

    q <= s & r <= s implies not [.r, s.] c= ].p, q.[

    proof

      assume that

       A1: q <= s and

       A2: r <= s;

      take t = s;

      thus t in [.r, s.] by A2, Th1;

      thus thesis by A1, Th4;

    end;

    theorem :: XXREAL_1:125

    q < s & r < s implies not [.r, s.[ c= ].p, q.[

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in [.r, s.[ by A5, Th3;

        thus thesis by A4, Th4;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in [.r, s.[ by A7, A8, Th3;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th4;

      end;

    end;

    theorem :: XXREAL_1:126

    q <= s & r < s implies not ].r, s.] c= ].p, q.[

    proof

      assume that

       A1: q <= s and

       A2: r < s;

      take t = s;

      thus t in ].r, s.] by A2, Th2;

      thus thesis by A1, Th4;

    end;

    theorem :: XXREAL_1:127

    q < s & r < s implies not ].r, s.[ c= ].p, q.[

    proof

      assume that

       A1: q < s and

       A2: r < s;

      per cases ;

        suppose

         A3: r <= q;

        consider t such that

         A4: q < t and

         A5: t < s by A1, XREAL_1: 227;

        take t;

        r < t by A3, A4, XXREAL_0: 2;

        hence t in ].r, s.[ by A5, Th4;

        thus thesis by A4, Th4;

      end;

        suppose

         A6: q < r;

        consider t such that

         A7: r < t and

         A8: t < s by A2, XREAL_1: 227;

        take t;

        thus t in ].r, s.[ by A7, A8, Th4;

        q < t by A6, A7, XXREAL_0: 2;

        hence thesis by Th4;

      end;

    end;

    begin

    theorem :: XXREAL_1:128

    

     Th128: r <= s implies [.r, s.] = ( ].r, s.[ \/ {r, s})

    proof

      assume

       A1: r <= s;

      let t;

      thus t in [.r, s.] implies t in ( ].r, s.[ \/ {r, s})

      proof

        assume t in [.r, s.];

        then t in ].r, s.[ or t = r or t = s by Th5;

        then t in ].r, s.[ or t in {r, s} by TARSKI:def 2;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( ].r, s.[ \/ {r, s});

      then t in ].r, s.[ or t in {r, s} by XBOOLE_0:def 3;

      then t in ].r, s.[ or t = r or t = s by TARSKI:def 2;

      hence thesis by A1, Th1, Th16;

    end;

    theorem :: XXREAL_1:129

    

     Th129: r <= s implies [.r, s.] = ( [.r, s.[ \/ {s})

    proof

      assume

       A1: r <= s;

      let t;

      thus t in [.r, s.] implies t in ( [.r, s.[ \/ {s})

      proof

        assume t in [.r, s.];

        then t in [.r, s.[ or t = s by Th7;

        then t in [.r, s.[ or t in {s} by TARSKI:def 1;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( [.r, s.[ \/ {s});

      then t in [.r, s.[ or t in {s} by XBOOLE_0:def 3;

      then t in [.r, s.[ or t = s by TARSKI:def 1;

      hence thesis by A1, Th1, Th13;

    end;

    theorem :: XXREAL_1:130

    

     Th130: r <= s implies [.r, s.] = ( {r} \/ ].r, s.])

    proof

      assume

       A1: r <= s;

      let t;

      thus t in [.r, s.] implies t in ( {r} \/ ].r, s.])

      proof

        assume t in [.r, s.];

        then t in ].r, s.] or t = r by Th6;

        then t in ].r, s.] or t in {r} by TARSKI:def 1;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( {r} \/ ].r, s.]);

      then t in ].r, s.] or t in {r} by XBOOLE_0:def 3;

      then t in ].r, s.] or t = r by TARSKI:def 1;

      hence thesis by A1, Th1, Th12;

    end;

    theorem :: XXREAL_1:131

    

     Th131: r < s implies [.r, s.[ = ( {r} \/ ].r, s.[)

    proof

      assume

       A1: r < s;

      let t;

      thus t in [.r, s.[ implies t in ( {r} \/ ].r, s.[)

      proof

        assume t in [.r, s.[;

        then t in ].r, s.[ or t = r by Th8;

        then t in ].r, s.[ or t in {r} by TARSKI:def 1;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( {r} \/ ].r, s.[);

      then t in ].r, s.[ or t in {r} by XBOOLE_0:def 3;

      then t in ].r, s.[ or t = r by TARSKI:def 1;

      hence thesis by A1, Th3, Th14;

    end;

    theorem :: XXREAL_1:132

    

     Th132: r < s implies ].r, s.] = ( ].r, s.[ \/ {s})

    proof

      assume

       A1: r < s;

      let t;

      thus t in ].r, s.] implies t in ( ].r, s.[ \/ {s})

      proof

        assume t in ].r, s.];

        then t in ].r, s.[ or t = s by Th9;

        then t in ].r, s.[ or t in {s} by TARSKI:def 1;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( ].r, s.[ \/ {s});

      then t in ].r, s.[ or t in {s} by XBOOLE_0:def 3;

      then t in ].r, s.[ or t = s by TARSKI:def 1;

      hence thesis by A1, Th2, Th15;

    end;

    theorem :: XXREAL_1:133

    r <= s implies ( [.r, s.] \ {r, s}) = ].r, s.[

    proof

      assume r <= s;

      then

       A1: [.r, s.] = ( ].r, s.[ \/ {r, s}) by Th128;

      

       A2: not r in ].r, s.[ by Th4;

       not s in ].r, s.[ by Th4;

      hence thesis by A1, A2, ZFMISC_1: 121;

    end;

    theorem :: XXREAL_1:134

    r <= s implies ( [.r, s.] \ {r}) = ].r, s.]

    proof

      assume r <= s;

      then

       A1: [.r, s.] = ( {r} \/ ].r, s.]) by Th130;

       not r in ].r, s.] by Th2;

      hence thesis by A1, ZFMISC_1: 117;

    end;

    theorem :: XXREAL_1:135

    r <= s implies ( [.r, s.] \ {s}) = [.r, s.[

    proof

      assume r <= s;

      then

       A1: [.r, s.] = ( [.r, s.[ \/ {s}) by Th129;

       not s in [.r, s.[ by Th3;

      hence thesis by A1, ZFMISC_1: 117;

    end;

    theorem :: XXREAL_1:136

    r < s implies ( [.r, s.[ \ {r}) = ].r, s.[

    proof

      assume r < s;

      then

       A1: [.r, s.[ = ( {r} \/ ].r, s.[) by Th131;

       not r in ].r, s.[ by Th4;

      hence thesis by A1, ZFMISC_1: 117;

    end;

    theorem :: XXREAL_1:137

    r < s implies ( ].r, s.] \ {s}) = ].r, s.[

    proof

      assume r < s;

      then

       A1: ].r, s.] = ( ].r, s.[ \/ {s}) by Th132;

       not s in ].r, s.[ by Th4;

      hence thesis by A1, ZFMISC_1: 117;

    end;

    theorem :: XXREAL_1:138

    r < s & s < t implies ( ].r, s.] /\ [.s, t.[) = {s}

    proof

      assume that

       A1: r < s and

       A2: s < t;

      now

        let x be object;

        hereby

          assume

           A3: x in ( ].r, s.] /\ [.s, t.[);

          then

          reconsider p = x as ExtReal;

          

           A4: p in ].r, s.] by A3, XBOOLE_0:def 4;

          p in [.s, t.[ by A3, XBOOLE_0:def 4;

          then

           A5: s <= p by Th3;

          p <= s by A4, Th2;

          hence x = s by A5, XXREAL_0: 1;

        end;

        assume

         A6: x = s;

        

         A7: s in ].r, s.] by A1, Th2;

        s in [.s, t.[ by A2, Th3;

        hence x in ( ].r, s.] /\ [.s, t.[) by A6, A7, XBOOLE_0:def 4;

      end;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:139

    ( [.r, s.[ /\ [.p, q.[) = [.( max (r,p)), ( min (s,q)).[

    proof

      let t;

      thus t in ( [.r, s.[ /\ [.p, q.[) implies t in [.( max (r,p)), ( min (s,q)).[

      proof

        assume

         A1: t in ( [.r, s.[ /\ [.p, q.[);

        then

         A2: t in [.r, s.[ by XBOOLE_0:def 4;

        

         A3: t in [.p, q.[ by A1, XBOOLE_0:def 4;

        

         A4: r <= t by A2, Th3;

        

         A5: t < s by A2, Th3;

        

         A6: p <= t by A3, Th3;

        

         A7: t < q by A3, Th3;

        

         A8: ( max (r,p)) <= t by A4, A6, XXREAL_0: 28;

        t < ( min (s,q)) by A5, A7, XXREAL_0: 21;

        hence thesis by A8, Th3;

      end;

      assume

       A9: t in [.( max (r,p)), ( min (s,q)).[;

      then

       A10: ( max (r,p)) <= t by Th3;

      

       A11: t < ( min (s,q)) by A9, Th3;

      

       A12: r <= t by A10, XXREAL_0: 30;

      

       A13: p <= t by A10, XXREAL_0: 30;

      

       A14: t < s by A11, XXREAL_0: 23;

      

       A15: t < q by A11, XXREAL_0: 23;

      

       A16: t in [.r, s.[ by A12, A14, Th3;

      t in [.p, q.[ by A13, A15, Th3;

      hence thesis by A16, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:140

    ( [.r, s.] /\ [.p, q.]) = [.( max (r,p)), ( min (s,q)).]

    proof

      let t;

      thus t in ( [.r, s.] /\ [.p, q.]) implies t in [.( max (r,p)), ( min (s,q)).]

      proof

        assume

         A1: t in ( [.r, s.] /\ [.p, q.]);

        then

         A2: t in [.r, s.] by XBOOLE_0:def 4;

        

         A3: t in [.p, q.] by A1, XBOOLE_0:def 4;

        

         A4: r <= t by A2, Th1;

        

         A5: t <= s by A2, Th1;

        

         A6: p <= t by A3, Th1;

        

         A7: t <= q by A3, Th1;

        

         A8: ( max (r,p)) <= t by A4, A6, XXREAL_0: 28;

        t <= ( min (s,q)) by A5, A7, XXREAL_0: 20;

        hence thesis by A8, Th1;

      end;

      assume

       A9: t in [.( max (r,p)), ( min (s,q)).];

      then

       A10: ( max (r,p)) <= t by Th1;

      

       A11: t <= ( min (s,q)) by A9, Th1;

      

       A12: r <= t by A10, XXREAL_0: 30;

      

       A13: p <= t by A10, XXREAL_0: 30;

      

       A14: t <= s by A11, XXREAL_0: 22;

      

       A15: t <= q by A11, XXREAL_0: 22;

      

       A16: t in [.r, s.] by A12, A14, Th1;

      t in [.p, q.] by A13, A15, Th1;

      hence thesis by A16, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:141

    ( ].r, s.] /\ ].p, q.]) = ].( max (r,p)), ( min (s,q)).]

    proof

      let t;

      thus t in ( ].r, s.] /\ ].p, q.]) implies t in ].( max (r,p)), ( min (s,q)).]

      proof

        assume

         A1: t in ( ].r, s.] /\ ].p, q.]);

        then

         A2: t in ].r, s.] by XBOOLE_0:def 4;

        

         A3: t in ].p, q.] by A1, XBOOLE_0:def 4;

        

         A4: r < t by A2, Th2;

        

         A5: t <= s by A2, Th2;

        

         A6: p < t by A3, Th2;

        

         A7: t <= q by A3, Th2;

        

         A8: ( max (r,p)) < t by A4, A6, XXREAL_0: 29;

        t <= ( min (s,q)) by A5, A7, XXREAL_0: 20;

        hence thesis by A8, Th2;

      end;

      assume

       A9: t in ].( max (r,p)), ( min (s,q)).];

      then

       A10: ( max (r,p)) < t by Th2;

      

       A11: t <= ( min (s,q)) by A9, Th2;

      

       A12: r < t by A10, XXREAL_0: 31;

      

       A13: p < t by A10, XXREAL_0: 31;

      

       A14: t <= s by A11, XXREAL_0: 22;

      

       A15: t <= q by A11, XXREAL_0: 22;

      

       A16: t in ].r, s.] by A12, A14, Th2;

      t in ].p, q.] by A13, A15, Th2;

      hence thesis by A16, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:142

    ( ].r, s.[ /\ ].p, q.[) = ].( max (r,p)), ( min (s,q)).[

    proof

      let t;

      thus t in ( ].r, s.[ /\ ].p, q.[) implies t in ].( max (r,p)), ( min (s,q)).[

      proof

        assume

         A1: t in ( ].r, s.[ /\ ].p, q.[);

        then

         A2: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A3: t in ].p, q.[ by A1, XBOOLE_0:def 4;

        

         A4: r < t by A2, Th4;

        

         A5: t < s by A2, Th4;

        

         A6: p < t by A3, Th4;

        

         A7: t < q by A3, Th4;

        

         A8: ( max (r,p)) < t by A4, A6, XXREAL_0: 29;

        t < ( min (s,q)) by A5, A7, XXREAL_0: 21;

        hence thesis by A8, Th4;

      end;

      assume

       A9: t in ].( max (r,p)), ( min (s,q)).[;

      then

       A10: ( max (r,p)) < t by Th4;

      

       A11: t < ( min (s,q)) by A9, Th4;

      

       A12: r < t by A10, XXREAL_0: 31;

      

       A13: p < t by A10, XXREAL_0: 31;

      

       A14: t < s by A11, XXREAL_0: 23;

      

       A15: t < q by A11, XXREAL_0: 23;

      

       A16: t in ].r, s.[ by A12, A14, Th4;

      t in ].p, q.[ by A13, A15, Th4;

      hence thesis by A16, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:143

    r <= p & s <= q implies ( [.r, s.] /\ [.p, q.]) = [.p, s.]

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( [.r, s.] /\ [.p, q.]) implies t in [.p, s.]

      proof

        assume

         A3: t in ( [.r, s.] /\ [.p, q.]);

        then

         A4: t in [.r, s.] by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t <= s by A4, Th1;

        p <= t by A5, Th1;

        hence thesis by A6, Th1;

      end;

      assume

       A7: t in [.p, s.];

      then

       A8: p <= t by Th1;

      

       A9: t <= s by A7, Th1;

      

       A10: r <= t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in [.r, s.] by A9, A10, Th1;

      t in [.p, q.] by A8, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:144

    r <= p & s <= q implies ( [.r, s.[ /\ [.p, q.]) = [.p, s.[

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( [.r, s.[ /\ [.p, q.]) implies t in [.p, s.[

      proof

        assume

         A3: t in ( [.r, s.[ /\ [.p, q.]);

        then

         A4: t in [.r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th3;

        p <= t by A5, Th1;

        hence thesis by A6, Th3;

      end;

      assume

       A7: t in [.p, s.[;

      then

       A8: p <= t by Th3;

      

       A9: t < s by A7, Th3;

      

       A10: r <= t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in [.r, s.[ by A9, A10, Th3;

      t in [.p, q.] by A8, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:145

    r >= p & s > q implies ( [.r, s.[ /\ [.p, q.]) = [.r, q.]

    proof

      assume that

       A1: r >= p and

       A2: s > q;

      let t;

      thus t in ( [.r, s.[ /\ [.p, q.]) implies t in [.r, q.]

      proof

        assume

         A3: t in ( [.r, s.[ /\ [.p, q.]);

        then

         A4: t in [.r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: r <= t by A4, Th3;

        t <= q by A5, Th1;

        hence thesis by A6, Th1;

      end;

      assume

       A7: t in [.r, q.];

      then

       A8: r <= t by Th1;

      

       A9: t <= q by A7, Th1;

      then

       A10: t < s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in [.r, s.[ by A8, A10, Th3;

      t in [.p, q.] by A9, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:146

    r < p & s <= q implies ( ].r, s.] /\ [.p, q.]) = [.p, s.]

    proof

      assume that

       A1: r < p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.] /\ [.p, q.]) implies t in [.p, s.]

      proof

        assume

         A3: t in ( ].r, s.] /\ [.p, q.]);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t <= s by A4, Th2;

        p <= t by A5, Th1;

        hence thesis by A6, Th1;

      end;

      assume

       A7: t in [.p, s.];

      then

       A8: p <= t by Th1;

      

       A9: t <= s by A7, Th1;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A9, A10, Th2;

      t in [.p, q.] by A8, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:147

    r >= p & s >= q implies ( ].r, s.] /\ [.p, q.]) = ].r, q.]

    proof

      assume that

       A1: r >= p and

       A2: s >= q;

      let t;

      thus t in ( ].r, s.] /\ [.p, q.]) implies t in ].r, q.]

      proof

        assume

         A3: t in ( ].r, s.] /\ [.p, q.]);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th2;

        t <= q by A5, Th1;

        hence thesis by A6, Th2;

      end;

      assume

       A7: t in ].r, q.];

      then

       A8: r < t by Th2;

      

       A9: t <= q by A7, Th2;

      then

       A10: t <= s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A8, A10, Th2;

      t in [.p, q.] by A9, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:148

    r < p & s <= q implies ( ].r, s.[ /\ [.p, q.]) = [.p, s.[

    proof

      assume that

       A1: r < p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.[ /\ [.p, q.]) implies t in [.p, s.[

      proof

        assume

         A3: t in ( ].r, s.[ /\ [.p, q.]);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th4;

        p <= t by A5, Th1;

        hence thesis by A6, Th3;

      end;

      assume

       A7: t in [.p, s.[;

      then

       A8: p <= t by Th3;

      

       A9: t < s by A7, Th3;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A9, A10, Th4;

      t in [.p, q.] by A8, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:149

    r >= p & s > q implies ( ].r, s.[ /\ [.p, q.]) = ].r, q.]

    proof

      assume that

       A1: r >= p and

       A2: s > q;

      let t;

      thus t in ( ].r, s.[ /\ [.p, q.]) implies t in ].r, q.]

      proof

        assume

         A3: t in ( ].r, s.[ /\ [.p, q.]);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.] by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th4;

        t <= q by A5, Th1;

        hence thesis by A6, Th2;

      end;

      assume

       A7: t in ].r, q.];

      then

       A8: r < t by Th2;

      

       A9: t <= q by A7, Th2;

      then

       A10: t < s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A8, A10, Th4;

      t in [.p, q.] by A9, A11, Th1;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:150

    r <= p & s <= q implies ( [.r, s.[ /\ [.p, q.[) = [.p, s.[

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( [.r, s.[ /\ [.p, q.[) implies t in [.p, s.[

      proof

        assume

         A3: t in ( [.r, s.[ /\ [.p, q.[);

        then

         A4: t in [.r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th3;

        p <= t by A5, Th3;

        hence thesis by A6, Th3;

      end;

      assume

       A7: t in [.p, s.[;

      then

       A8: p <= t by Th3;

      

       A9: t < s by A7, Th3;

      

       A10: r <= t by A1, A8, XXREAL_0: 2;

      

       A11: t < q by A2, A9, XXREAL_0: 2;

      

       A12: t in [.r, s.[ by A9, A10, Th3;

      t in [.p, q.[ by A8, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:151

    r >= p & s >= q implies ( [.r, s.[ /\ [.p, q.[) = [.r, q.[

    proof

      assume that

       A1: r >= p and

       A2: s >= q;

      let t;

      thus t in ( [.r, s.[ /\ [.p, q.[) implies t in [.r, q.[

      proof

        assume

         A3: t in ( [.r, s.[ /\ [.p, q.[);

        then

         A4: t in [.r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: r <= t by A4, Th3;

        t < q by A5, Th3;

        hence thesis by A6, Th3;

      end;

      assume

       A7: t in [.r, q.[;

      then

       A8: r <= t by Th3;

      

       A9: t < q by A7, Th3;

      then

       A10: t < s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in [.r, s.[ by A8, A10, Th3;

      t in [.p, q.[ by A9, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:152

    

     Th152: r < p & s < q implies ( ].r, s.] /\ [.p, q.[) = [.p, s.]

    proof

      assume that

       A1: r < p and

       A2: s < q;

      let t;

      thus t in ( ].r, s.] /\ [.p, q.[) implies t in [.p, s.]

      proof

        assume

         A3: t in ( ].r, s.] /\ [.p, q.[);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: t <= s by A4, Th2;

        p <= t by A5, Th3;

        hence thesis by A6, Th1;

      end;

      assume

       A7: t in [.p, s.];

      then

       A8: p <= t by Th1;

      

       A9: t <= s by A7, Th1;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t < q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A9, A10, Th2;

      t in [.p, q.[ by A8, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:153

    r >= p & s >= q implies ( ].r, s.] /\ [.p, q.[) = ].r, q.[

    proof

      assume that

       A1: r >= p and

       A2: s >= q;

      let t;

      thus t in ( ].r, s.] /\ [.p, q.[) implies t in ].r, q.[

      proof

        assume

         A3: t in ( ].r, s.] /\ [.p, q.[);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th2;

        t < q by A5, Th3;

        hence thesis by A6, Th4;

      end;

      assume

       A7: t in ].r, q.[;

      then

       A8: r < t by Th4;

      

       A9: t < q by A7, Th4;

      then

       A10: t <= s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A8, A10, Th2;

      t in [.p, q.[ by A9, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:154

    

     Th154: r < p & s <= q implies ( ].r, s.[ /\ [.p, q.[) = [.p, s.[

    proof

      assume that

       A1: r < p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.[ /\ [.p, q.[) implies t in [.p, s.[

      proof

        assume

         A3: t in ( ].r, s.[ /\ [.p, q.[);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th4;

        p <= t by A5, Th3;

        hence thesis by A6, Th3;

      end;

      assume

       A7: t in [.p, s.[;

      then

       A8: p <= t by Th3;

      

       A9: t < s by A7, Th3;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t < q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A9, A10, Th4;

      t in [.p, q.[ by A8, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:155

    r >= p & s >= q implies ( ].r, s.[ /\ [.p, q.[) = ].r, q.[

    proof

      assume that

       A1: r >= p and

       A2: s >= q;

      let t;

      thus t in ( ].r, s.[ /\ [.p, q.[) implies t in ].r, q.[

      proof

        assume

         A3: t in ( ].r, s.[ /\ [.p, q.[);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in [.p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th4;

        t < q by A5, Th3;

        hence thesis by A6, Th4;

      end;

      assume

       A7: t in ].r, q.[;

      then

       A8: r < t by Th4;

      

       A9: t < q by A7, Th4;

      then

       A10: t < s by A2, XXREAL_0: 2;

      

       A11: p <= t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A8, A10, Th4;

      t in [.p, q.[ by A9, A11, Th3;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:156

    r <= p & s <= q implies ( ].r, s.] /\ ].p, q.]) = ].p, s.]

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.] /\ ].p, q.]) implies t in ].p, s.]

      proof

        assume

         A3: t in ( ].r, s.] /\ ].p, q.]);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in ].p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t <= s by A4, Th2;

        p < t by A5, Th2;

        hence thesis by A6, Th2;

      end;

      assume

       A7: t in ].p, s.];

      then

       A8: p < t by Th2;

      

       A9: t <= s by A7, Th2;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A9, A10, Th2;

      t in ].p, q.] by A8, A11, Th2;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:157

    r >= p & s >= q implies ( ].r, s.] /\ ].p, q.]) = ].r, q.]

    proof

      assume that

       A1: r >= p and

       A2: s >= q;

      let t;

      thus t in ( ].r, s.] /\ ].p, q.]) implies t in ].r, q.]

      proof

        assume

         A3: t in ( ].r, s.] /\ ].p, q.]);

        then

         A4: t in ].r, s.] by XBOOLE_0:def 4;

        

         A5: t in ].p, q.] by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th2;

        t <= q by A5, Th2;

        hence thesis by A6, Th2;

      end;

      assume

       A7: t in ].r, q.];

      then

       A8: r < t by Th2;

      

       A9: t <= q by A7, Th2;

      then

       A10: t <= s by A2, XXREAL_0: 2;

      

       A11: p < t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.] by A8, A10, Th2;

      t in ].p, q.] by A9, A11, Th2;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:158

    r <= p & s <= q implies ( ].r, s.[ /\ ].p, q.]) = ].p, s.[

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.[ /\ ].p, q.]) implies t in ].p, s.[

      proof

        assume

         A3: t in ( ].r, s.[ /\ ].p, q.]);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in ].p, q.] by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th4;

        p < t by A5, Th2;

        hence thesis by A6, Th4;

      end;

      assume

       A7: t in ].p, s.[;

      then

       A8: p < t by Th4;

      

       A9: t < s by A7, Th4;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t <= q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A9, A10, Th4;

      t in ].p, q.] by A8, A11, Th2;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:159

    

     Th159: r >= p & s > q implies ( ].r, s.[ /\ ].p, q.]) = ].r, q.]

    proof

      assume that

       A1: r >= p and

       A2: s > q;

      let t;

      thus t in ( ].r, s.[ /\ ].p, q.]) implies t in ].r, q.]

      proof

        assume

         A3: t in ( ].r, s.[ /\ ].p, q.]);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in ].p, q.] by A3, XBOOLE_0:def 4;

        

         A6: r < t by A4, Th4;

        t <= q by A5, Th2;

        hence thesis by A6, Th2;

      end;

      assume

       A7: t in ].r, q.];

      then

       A8: r < t by Th2;

      

       A9: t <= q by A7, Th2;

      then

       A10: t < s by A2, XXREAL_0: 2;

      

       A11: p < t by A1, A8, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A8, A10, Th4;

      t in ].p, q.] by A9, A11, Th2;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:160

    

     Th160: r <= p & s <= q implies ( ].r, s.[ /\ ].p, q.[) = ].p, s.[

    proof

      assume that

       A1: r <= p and

       A2: s <= q;

      let t;

      thus t in ( ].r, s.[ /\ ].p, q.[) implies t in ].p, s.[

      proof

        assume

         A3: t in ( ].r, s.[ /\ ].p, q.[);

        then

         A4: t in ].r, s.[ by XBOOLE_0:def 4;

        

         A5: t in ].p, q.[ by A3, XBOOLE_0:def 4;

        

         A6: t < s by A4, Th4;

        p < t by A5, Th4;

        hence thesis by A6, Th4;

      end;

      assume

       A7: t in ].p, s.[;

      then

       A8: p < t by Th4;

      

       A9: t < s by A7, Th4;

      

       A10: r < t by A1, A8, XXREAL_0: 2;

      

       A11: t < q by A2, A9, XXREAL_0: 2;

      

       A12: t in ].r, s.[ by A9, A10, Th4;

      t in ].p, q.[ by A8, A11, Th4;

      hence thesis by A12, XBOOLE_0:def 4;

    end;

    theorem :: XXREAL_1:161

    ( [.r, s.[ \/ [.p, q.[) c= [.( min (r,p)), ( max (s,q)).[

    proof

      let t;

      assume t in ( [.r, s.[ \/ [.p, q.[);

      then t in [.r, s.[ or t in [.p, q.[ by XBOOLE_0:def 3;

      then

       A1: r <= t & t < s or p <= t & t < q by Th3;

      then

       A2: ( min (r,p)) <= t by XXREAL_0: 23;

      t < ( max (s,q)) by A1, XXREAL_0: 30;

      hence thesis by A2, Th3;

    end;

    theorem :: XXREAL_1:162

     [.r, s.[ meets [.p, q.[ implies ( [.r, s.[ \/ [.p, q.[) = [.( min (r,p)), ( max (s,q)).[

    proof

      assume [.r, s.[ meets [.p, q.[;

      then

      consider u such that

       A1: u in [.r, s.[ and

       A2: u in [.p, q.[;

      let t;

      thus t in ( [.r, s.[ \/ [.p, q.[) implies t in [.( min (r,p)), ( max (s,q)).[

      proof

        assume t in ( [.r, s.[ \/ [.p, q.[);

        then t in [.r, s.[ or t in [.p, q.[ by XBOOLE_0:def 3;

        then

         A3: r <= t & t < s or p <= t & t < q by Th3;

        then

         A4: ( min (r,p)) <= t by XXREAL_0: 23;

        t < ( max (s,q)) by A3, XXREAL_0: 30;

        hence thesis by A4, Th3;

      end;

      

       A5: r <= u by A1, Th3;

      

       A6: u < s by A1, Th3;

      

       A7: p <= u by A2, Th3;

      

       A8: u < q by A2, Th3;

      assume

       A9: t in [.( min (r,p)), ( max (s,q)).[;

      then

       A10: ( min (r,p)) <= t by Th3;

      

       A11: t < ( max (s,q)) by A9, Th3;

      per cases by A10, A11, XXREAL_0: 21, XXREAL_0: 28;

        suppose r <= t & t < s or p <= t & t < q;

        then t in [.r, s.[ or t in [.p, q.[ by Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

        suppose that

         A12: p <= t and

         A13: t < s;

        u <= t or t <= u;

        then r <= t or t < q by A5, A8, XXREAL_0: 2;

        then t in [.r, s.[ or t in [.p, q.[ by A12, A13, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

        suppose that

         A14: r <= t and

         A15: t < q;

        u <= t or t <= u;

        then t < s or p <= t by A6, A7, XXREAL_0: 2;

        then t in [.r, s.[ or t in [.p, q.[ by A14, A15, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

    end;

    theorem :: XXREAL_1:163

    ( ].r, s.] \/ ].p, q.]) c= ].( min (r,p)), ( max (s,q)).]

    proof

      let t;

      assume t in ( ].r, s.] \/ ].p, q.]);

      then t in ].r, s.] or t in ].p, q.] by XBOOLE_0:def 3;

      then

       A1: r < t & t <= s or p < t & t <= q by Th2;

      then

       A2: ( min (r,p)) < t by XXREAL_0: 22;

      t <= ( max (s,q)) by A1, XXREAL_0: 31;

      hence thesis by A2, Th2;

    end;

    theorem :: XXREAL_1:164

     ].r, s.] meets ].p, q.] implies ( ].r, s.] \/ ].p, q.]) = ].( min (r,p)), ( max (s,q)).]

    proof

      assume ].r, s.] meets ].p, q.];

      then

      consider u such that

       A1: u in ].r, s.] and

       A2: u in ].p, q.];

      let t;

      thus t in ( ].r, s.] \/ ].p, q.]) implies t in ].( min (r,p)), ( max (s,q)).]

      proof

        assume t in ( ].r, s.] \/ ].p, q.]);

        then t in ].r, s.] or t in ].p, q.] by XBOOLE_0:def 3;

        then

         A3: r < t & t <= s or p < t & t <= q by Th2;

        then

         A4: ( min (r,p)) < t by XXREAL_0: 22;

        t <= ( max (s,q)) by A3, XXREAL_0: 31;

        hence thesis by A4, Th2;

      end;

      

       A5: r < u by A1, Th2;

      

       A6: u <= s by A1, Th2;

      

       A7: p < u by A2, Th2;

      

       A8: u <= q by A2, Th2;

      assume

       A9: t in ].( min (r,p)), ( max (s,q)).];

      then

       A10: ( min (r,p)) < t by Th2;

      

       A11: t <= ( max (s,q)) by A9, Th2;

      per cases by A10, A11, XXREAL_0: 20, XXREAL_0: 29;

        suppose r < t & t <= s or p < t & t <= q;

        then t in ].r, s.] or t in ].p, q.] by Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

        suppose that

         A12: p < t and

         A13: t <= s;

        u <= t or t <= u;

        then r < t or t <= q by A5, A8, XXREAL_0: 2;

        then t in ].r, s.] or t in ].p, q.] by A12, A13, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

        suppose that

         A14: r < t and

         A15: t <= q;

        u <= t or t <= u;

        then t <= s or p < t by A6, A7, XXREAL_0: 2;

        then t in ].r, s.] or t in ].p, q.] by A14, A15, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

    end;

    theorem :: XXREAL_1:165

    r <= s & s <= t implies ( [.r, s.] \/ [.s, t.]) = [.r, t.]

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( [.r, s.] \/ [.s, t.]) implies p in [.r, t.]

      proof

        assume p in ( [.r, s.] \/ [.s, t.]);

        then p in [.r, s.] or p in [.s, t.] by XBOOLE_0:def 3;

        then

         A3: r <= p & p <= s or s <= p & p <= t by Th1;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p <= t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th1;

      end;

      assume p in [.r, t.];

      then r <= p & p <= s or s <= p & p <= t by Th1;

      then p in [.r, s.] or p in [.s, t.] by Th1;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:166

    

     Th166: r <= s & s <= t implies ( [.r, s.[ \/ [.s, t.]) = [.r, t.]

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( [.r, s.[ \/ [.s, t.]) implies p in [.r, t.]

      proof

        assume p in ( [.r, s.[ \/ [.s, t.]);

        then p in [.r, s.[ or p in [.s, t.] by XBOOLE_0:def 3;

        then

         A3: r <= p & p < s or s <= p & p <= t by Th1, Th3;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p <= t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th1;

      end;

      assume p in [.r, t.];

      then r <= p & p < s or s <= p & p <= t by Th1;

      then p in [.r, s.[ or p in [.s, t.] by Th1, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:167

    

     Th167: r <= s & s <= t implies ( [.r, s.] \/ ].s, t.]) = [.r, t.]

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( [.r, s.] \/ ].s, t.]) implies p in [.r, t.]

      proof

        assume p in ( [.r, s.] \/ ].s, t.]);

        then p in [.r, s.] or p in ].s, t.] by XBOOLE_0:def 3;

        then

         A3: r <= p & p <= s or s < p & p <= t by Th1, Th2;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p <= t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th1;

      end;

      assume p in [.r, t.];

      then r <= p & p <= s or s < p & p <= t by Th1;

      then p in [.r, s.] or p in ].s, t.] by Th1, Th2;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:168

    r <= s & s <= t implies ( [.r, s.[ \/ [.s, t.[) = [.r, t.[

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( [.r, s.[ \/ [.s, t.[) implies p in [.r, t.[

      proof

        assume p in ( [.r, s.[ \/ [.s, t.[);

        then p in [.r, s.[ or p in [.s, t.[ by XBOOLE_0:def 3;

        then

         A3: r <= p & p < s or s <= p & p < t by Th3;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th3;

      end;

      assume p in [.r, t.[;

      then r <= p & p < s or s <= p & p < t by Th3;

      then p in [.r, s.[ or p in [.s, t.[ by Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:169

    

     Th169: r <= s & s < t implies ( [.r, s.] \/ ].s, t.[) = [.r, t.[

    proof

      assume that

       A1: r <= s and

       A2: s < t;

      let p;

      thus p in ( [.r, s.] \/ ].s, t.[) implies p in [.r, t.[

      proof

        assume p in ( [.r, s.] \/ ].s, t.[);

        then p in [.r, s.] or p in ].s, t.[ by XBOOLE_0:def 3;

        then

         A3: r <= p & p <= s or s < p & p < t by Th1, Th4;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th3;

      end;

      assume p in [.r, t.[;

      then r <= p & p <= s or s < p & p < t by Th3;

      then p in [.r, s.] or p in ].s, t.[ by Th1, Th4;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:170

    r <= s & s <= t implies ( ].r, s.] \/ ].s, t.]) = ].r, t.]

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( ].r, s.] \/ ].s, t.]) implies p in ].r, t.]

      proof

        assume p in ( ].r, s.] \/ ].s, t.]);

        then p in ].r, s.] or p in ].s, t.] by XBOOLE_0:def 3;

        then

         A3: r < p & p <= s or s < p & p <= t by Th2;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p <= t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th2;

      end;

      assume p in ].r, t.];

      then r < p & p <= s or s < p & p <= t by Th2;

      then p in ].r, s.] or p in ].s, t.] by Th2;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:171

    

     Th171: r <= s & s < t implies ( ].r, s.] \/ ].s, t.[) = ].r, t.[

    proof

      assume that

       A1: r <= s and

       A2: s < t;

      let p;

      thus p in ( ].r, s.] \/ ].s, t.[) implies p in ].r, t.[

      proof

        assume p in ( ].r, s.] \/ ].s, t.[);

        then p in ].r, s.] or p in ].s, t.[ by XBOOLE_0:def 3;

        then

         A3: r < p & p <= s or s < p & p < t by Th2, Th4;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th4;

      end;

      assume p in ].r, t.[;

      then r < p & p <= s or s < p & p < t by Th4;

      then p in ].r, s.] or p in ].s, t.[ by Th2, Th4;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:172

    r < s & s < t implies ( ].r, s.] \/ [.s, t.[) = ].r, t.[

    proof

      assume that

       A1: r < s and

       A2: s < t;

      let p;

      thus p in ( ].r, s.] \/ [.s, t.[) implies p in ].r, t.[

      proof

        assume p in ( ].r, s.] \/ [.s, t.[);

        then p in ].r, s.] or p in [.s, t.[ by XBOOLE_0:def 3;

        then

         A3: r < p & p <= s or s <= p & p < t by Th2, Th3;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th4;

      end;

      assume p in ].r, t.[;

      then r < p & p <= s or s < p & p < t by Th4;

      then p in ].r, s.] or p in [.s, t.[ by Th2, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:173

    

     Th173: r < s & s < t implies ( ].r, s.[ \/ [.s, t.[) = ].r, t.[

    proof

      assume that

       A1: r < s and

       A2: s < t;

      let p;

      thus p in ( ].r, s.[ \/ [.s, t.[) implies p in ].r, t.[

      proof

        assume p in ( ].r, s.[ \/ [.s, t.[);

        then p in ].r, s.[ or p in [.s, t.[ by XBOOLE_0:def 3;

        then

         A3: r < p & p < s or s <= p & p < t by Th3, Th4;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th4;

      end;

      assume p in ].r, t.[;

      then r < p & p < s or s <= p & p < t by Th4;

      then p in ].r, s.[ or p in [.s, t.[ by Th3, Th4;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:174

    

     Th174: p <= s & r <= q & s <= r implies ( [.p, r.] \/ [.s, q.]) = [.p, q.]

    proof

      assume that

       A1: p <= s and

       A2: r <= q and

       A3: s <= r;

      let t;

      thus t in ( [.p, r.] \/ [.s, q.]) implies t in [.p, q.]

      proof

        assume t in ( [.p, r.] \/ [.s, q.]);

        then t in [.p, r.] or t in [.s, q.] by XBOOLE_0:def 3;

        then

         A4: p <= t & t <= r or s <= t & t <= q by Th1;

        then

         A5: p <= t by A1, XXREAL_0: 2;

        t <= q by A2, A4, XXREAL_0: 2;

        hence thesis by A5, Th1;

      end;

      assume t in [.p, q.];

      then p <= t & t <= r or s <= t & t <= q by A3, Th1, XXREAL_0: 2;

      then t in [.p, r.] or t in [.s, q.] by Th1;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:175

    

     Th175: p <= s & r <= q & s < r implies ( [.p, r.[ \/ ].s, q.]) = [.p, q.]

    proof

      assume that

       A1: p <= s and

       A2: r <= q and

       A3: s < r;

      let t;

      thus t in ( [.p, r.[ \/ ].s, q.]) implies t in [.p, q.]

      proof

        assume t in ( [.p, r.[ \/ ].s, q.]);

        then t in [.p, r.[ or t in ].s, q.] by XBOOLE_0:def 3;

        then

         A4: p <= t & t <= r or s <= t & t <= q by Th2, Th3;

        then

         A5: p <= t by A1, XXREAL_0: 2;

        t <= q by A2, A4, XXREAL_0: 2;

        hence thesis by A5, Th1;

      end;

      assume t in [.p, q.];

      then p <= t & t < r or s < t & t <= q by A3, Th1, XXREAL_0: 2;

      then t in [.p, r.[ or t in ].s, q.] by Th2, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:176

    p <= s & s <= r & r < q implies ( [.p, r.] \/ [.s, q.[) = [.p, q.[

    proof

      assume that

       A1: p <= s and

       A2: s <= r and

       A3: r < q;

      let t;

      thus t in ( [.p, r.] \/ [.s, q.[) implies t in [.p, q.[

      proof

        assume t in ( [.p, r.] \/ [.s, q.[);

        then t in [.p, r.] or t in [.s, q.[ by XBOOLE_0:def 3;

        then

         A4: p <= t & t <= r or s <= t & t < q by Th1, Th3;

        then

         A5: p <= t by A1, XXREAL_0: 2;

        t < q by A3, A4, XXREAL_0: 2;

        hence thesis by A5, Th3;

      end;

      assume t in [.p, q.[;

      then p <= t & t <= r or s <= t & t < q by A2, Th3, XXREAL_0: 2;

      then t in [.p, r.] or t in [.s, q.[ by Th1, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:177

    p < s & r <= q & s <= r implies ( ].p, r.] \/ [.s, q.]) = ].p, q.]

    proof

      assume that

       A1: p < s and

       A2: r <= q and

       A3: s <= r;

      let t;

      thus t in ( ].p, r.] \/ [.s, q.]) implies t in ].p, q.]

      proof

        assume t in ( ].p, r.] \/ [.s, q.]);

        then t in ].p, r.] or t in [.s, q.] by XBOOLE_0:def 3;

        then

         A4: p < t & t <= r or s <= t & t <= q by Th1, Th2;

        then

         A5: p < t by A1, XXREAL_0: 2;

        t <= q by A2, A4, XXREAL_0: 2;

        hence thesis by A5, Th2;

      end;

      assume t in ].p, q.];

      then p < t & t <= r or s <= t & t <= q by A3, Th2, XXREAL_0: 2;

      then t in ].p, r.] or t in [.s, q.] by Th1, Th2;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:178

    

     Th178: p < s & r < q & s <= r implies ( ].p, r.] \/ [.s, q.[) = ].p, q.[

    proof

      assume that

       A1: p < s and

       A2: r < q and

       A3: s <= r;

      let t;

      thus t in ( ].p, r.] \/ [.s, q.[) implies t in ].p, q.[

      proof

        assume t in ( ].p, r.] \/ [.s, q.[);

        then t in ].p, r.] or t in [.s, q.[ by XBOOLE_0:def 3;

        then

         A4: p < t & t <= r or s <= t & t < q by Th2, Th3;

        then

         A5: p < t by A1, XXREAL_0: 2;

        t < q by A2, A4, XXREAL_0: 2;

        hence thesis by A5, Th4;

      end;

      assume t in ].p, q.[;

      then p < t & t <= r or s <= t & t < q by A3, Th4, XXREAL_0: 2;

      then t in ].p, r.] or t in [.s, q.[ by Th2, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:179

    p <= r & p <= s & r <= q & s <= q implies (( [.p, r.[ \/ [.r, s.]) \/ ].s, q.]) = [.p, q.]

    proof

      assume that

       A1: p <= r and

       A2: p <= s and

       A3: r <= q and

       A4: s <= q;

      per cases ;

        suppose r <= s;

        

        hence (( [.p, r.[ \/ [.r, s.]) \/ ].s, q.]) = ( [.p, s.] \/ ].s, q.]) by A1, Th166

        .= [.p, q.] by A2, A4, Th167;

      end;

        suppose

         A5: s < r;

        

        hence (( [.p, r.[ \/ [.r, s.]) \/ ].s, q.]) = (( [.p, r.[ \/ {} ) \/ ].s, q.]) by Th29

        .= [.p, q.] by A2, A3, A5, Th175;

      end;

    end;

    theorem :: XXREAL_1:180

    p < r & p < s & r < q & s < q implies (( ].p, r.] \/ ].r, s.[) \/ [.s, q.[) = ].p, q.[

    proof

      assume that

       A1: p < r and

       A2: p < s and

       A3: r < q and

       A4: s < q;

      per cases ;

        suppose r < s;

        

        hence (( ].p, r.] \/ ].r, s.[) \/ [.s, q.[) = ( ].p, s.[ \/ [.s, q.[) by A1, Th171

        .= ].p, q.[ by A2, A4, Th173;

      end;

        suppose

         A5: s <= r;

        

        hence (( ].p, r.] \/ ].r, s.[) \/ [.s, q.[) = (( ].p, r.] \/ {} ) \/ [.s, q.[) by Th28

        .= ].p, q.[ by A2, A3, A5, Th178;

      end;

    end;

    theorem :: XXREAL_1:181

    p <= r & r <= s & s <= q implies (( [.p, r.] \/ ].r, s.[) \/ [.s, q.]) = [.p, q.]

    proof

      assume that

       A1: p <= r and

       A2: r <= s and

       A3: s <= q;

      

       A4: p <= s by A1, A2, XXREAL_0: 2;

      

       A5: r <= q by A2, A3, XXREAL_0: 2;

      per cases ;

        suppose r < s;

        

        hence (( [.p, r.] \/ ].r, s.[) \/ [.s, q.]) = ( [.p, s.[ \/ [.s, q.]) by A1, Th169

        .= [.p, q.] by A3, A4, Th166;

      end;

        suppose

         A6: s <= r;

        

        hence (( [.p, r.] \/ ].r, s.[) \/ [.s, q.]) = (( [.p, r.] \/ {} ) \/ [.s, q.]) by Th28

        .= [.p, q.] by A4, A5, A6, Th174;

      end;

    end;

    theorem :: XXREAL_1:182

    

     Th182: r <= s implies ( [.r, t.] \ [.r, s.]) = ].s, t.]

    proof

      assume that

       A1: r <= s;

      let p;

      thus p in ( [.r, t.] \ [.r, s.]) implies p in ].s, t.]

      proof

        assume

         A2: p in ( [.r, t.] \ [.r, s.]);

        then

         A3: not p in [.r, s.] by XBOOLE_0:def 5;

        

         A4: p <= t by A2, Th1;

        p < r or s < p by A3, Th1;

        hence thesis by A2, A4, Th1, Th2;

      end;

      assume

       A5: p in ].s, t.];

      then

       A6: s < p by Th2;

      then

       A7: r <= p by A1, XXREAL_0: 2;

      p <= t by A5, Th2;

      then

       A8: p in [.r, t.] by A7, Th1;

       not p in [.r, s.] by A6, Th1;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:183

    

     Th183: r <= s implies ( [.r, t.[ \ [.r, s.]) = ].s, t.[

    proof

      assume that

       A1: r <= s;

      let p;

      thus p in ( [.r, t.[ \ [.r, s.]) implies p in ].s, t.[

      proof

        assume

         A2: p in ( [.r, t.[ \ [.r, s.]);

        then

         A3: not p in [.r, s.] by XBOOLE_0:def 5;

        

         A4: p < t by A2, Th3;

        p < r or s < p by A3, Th1;

        hence thesis by A2, A4, Th3, Th4;

      end;

      assume

       A5: p in ].s, t.[;

      then

       A6: s < p by Th4;

      then

       A7: r <= p by A1, XXREAL_0: 2;

      p < t by A5, Th4;

      then

       A8: p in [.r, t.[ by A7, Th3;

       not p in [.r, s.] by A6, Th1;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:184

    

     Th184: r < s implies ( [.r, t.] \ [.r, s.[) = [.s, t.]

    proof

      assume that

       A1: r < s;

      let p;

      thus p in ( [.r, t.] \ [.r, s.[) implies p in [.s, t.]

      proof

        assume

         A2: p in ( [.r, t.] \ [.r, s.[);

        then

         A3: not p in [.r, s.[ by XBOOLE_0:def 5;

        

         A4: p <= t by A2, Th1;

        p < r or s <= p by A3, Th3;

        hence thesis by A2, A4, Th1;

      end;

      assume

       A5: p in [.s, t.];

      then

       A6: s <= p by Th1;

      then

       A7: r <= p by A1, XXREAL_0: 2;

      p <= t by A5, Th1;

      then

       A8: p in [.r, t.] by A7, Th1;

       not p in [.r, s.[ by A6, Th3;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:185

    

     Th185: r < s implies ( [.r, t.[ \ [.r, s.[) = [.s, t.[

    proof

      assume that

       A1: r < s;

      let p;

      thus p in ( [.r, t.[ \ [.r, s.[) implies p in [.s, t.[

      proof

        assume

         A2: p in ( [.r, t.[ \ [.r, s.[);

        then

         A3: not p in [.r, s.[ by XBOOLE_0:def 5;

        

         A4: p < t by A2, Th3;

        p < r or s <= p by A3, Th3;

        hence thesis by A2, A4, Th3;

      end;

      assume

       A5: p in [.s, t.[;

      then

       A6: s <= p by Th3;

      then

       A7: r <= p by A1, XXREAL_0: 2;

      p < t by A5, Th3;

      then

       A8: p in [.r, t.[ by A7, Th3;

       not p in [.r, s.[ by A6, Th3;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:186

    

     Th186: r <= s implies ( [.r, t.] \ [.r, s.]) = ].s, t.]

    proof

      assume that

       A1: r <= s;

      let p;

      thus p in ( [.r, t.] \ [.r, s.]) implies p in ].s, t.]

      proof

        assume

         A2: p in ( [.r, t.] \ [.r, s.]);

        then

         A3: not p in [.r, s.] by XBOOLE_0:def 5;

        

         A4: p <= t by A2, Th1;

        p < r or s < p by A3, Th1;

        hence thesis by A2, A4, Th1, Th2;

      end;

      assume

       A5: p in ].s, t.];

      then

       A6: s < p by Th2;

      then

       A7: r <= p by A1, XXREAL_0: 2;

      p <= t by A5, Th2;

      then

       A8: p in [.r, t.] by A7, Th1;

       not p in [.r, s.] by A6, Th1;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:187

    

     Th187: r < s implies ( ].r, t.[ \ ].r, s.]) = ].s, t.[

    proof

      assume that

       A1: r < s;

      let p;

      thus p in ( ].r, t.[ \ ].r, s.]) implies p in ].s, t.[

      proof

        assume

         A2: p in ( ].r, t.[ \ ].r, s.]);

        then

         A3: not p in ].r, s.] by XBOOLE_0:def 5;

        

         A4: p < t by A2, Th4;

        p <= r or s < p by A3, Th2;

        hence thesis by A2, A4, Th4;

      end;

      assume

       A5: p in ].s, t.[;

      then

       A6: s < p by Th4;

      then

       A7: r < p by A1, XXREAL_0: 2;

      p < t by A5, Th4;

      then

       A8: p in ].r, t.[ by A7, Th4;

       not p in ].r, s.] by A6, Th2;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:188

    

     Th188: r < s implies ( ].r, t.] \ ].r, s.[) = [.s, t.]

    proof

      assume that

       A1: r < s;

      let p;

      thus p in ( ].r, t.] \ ].r, s.[) implies p in [.s, t.]

      proof

        assume

         A2: p in ( ].r, t.] \ ].r, s.[);

        then

         A3: not p in ].r, s.[ by XBOOLE_0:def 5;

        

         A4: p <= t by A2, Th2;

        p <= r or s <= p by A3, Th4;

        hence thesis by A2, A4, Th1, Th2;

      end;

      assume

       A5: p in [.s, t.];

      then

       A6: s <= p by Th1;

      then

       A7: r < p by A1, XXREAL_0: 2;

      p <= t by A5, Th1;

      then

       A8: p in ].r, t.] by A7, Th2;

       not p in ].r, s.[ by A6, Th4;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:189

    

     Th189: r < s implies ( ].r, t.[ \ ].r, s.[) = [.s, t.[

    proof

      assume that

       A1: r < s;

      let p;

      thus p in ( ].r, t.[ \ ].r, s.[) implies p in [.s, t.[

      proof

        assume

         A2: p in ( ].r, t.[ \ ].r, s.[);

        then

         A3: not p in ].r, s.[ by XBOOLE_0:def 5;

        

         A4: p < t by A2, Th4;

        p <= r or s <= p by A3, Th4;

        hence thesis by A2, A4, Th3, Th4;

      end;

      assume

       A5: p in [.s, t.[;

      then

       A6: s <= p by Th3;

      then

       A7: r < p by A1, XXREAL_0: 2;

      p < t by A5, Th3;

      then

       A8: p in ].r, t.[ by A7, Th4;

       not p in ].r, s.[ by A6, Th4;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:190

    

     Th190: s <= t implies ( [.r, t.] \ [.s, t.]) = [.r, s.[

    proof

      assume that

       A1: s <= t;

      let p;

      thus p in ( [.r, t.] \ [.s, t.]) implies p in [.r, s.[

      proof

        assume

         A2: p in ( [.r, t.] \ [.s, t.]);

        then

         A3: not p in [.s, t.] by XBOOLE_0:def 5;

        

         A4: r <= p by A2, Th1;

        p < s or t < p by A3, Th1;

        hence thesis by A2, A4, Th1, Th3;

      end;

      assume

       A5: p in [.r, s.[;

      then

       A6: p < s by Th3;

      

       A7: r <= p by A5, Th3;

      p <= t by A1, A6, XXREAL_0: 2;

      then

       A8: p in [.r, t.] by A7, Th1;

       not p in [.s, t.] by A6, Th1;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:191

    

     Th191: s <= t implies ( ].r, t.] \ [.s, t.]) = ].r, s.[

    proof

      assume that

       A1: s <= t;

      let p;

      thus p in ( ].r, t.] \ [.s, t.]) implies p in ].r, s.[

      proof

        assume

         A2: p in ( ].r, t.] \ [.s, t.]);

        then

         A3: not p in [.s, t.] by XBOOLE_0:def 5;

        

         A4: r < p by A2, Th2;

        p < s or t < p by A3, Th1;

        hence thesis by A2, A4, Th2, Th4;

      end;

      assume

       A5: p in ].r, s.[;

      then

       A6: p < s by Th4;

      

       A7: r < p by A5, Th4;

      p <= t by A1, A6, XXREAL_0: 2;

      then

       A8: p in ].r, t.] by A7, Th2;

       not p in [.s, t.] by A6, Th1;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:192

    

     Th192: s < t implies ( [.r, t.] \ ].s, t.]) = [.r, s.]

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( [.r, t.] \ ].s, t.]) implies p in [.r, s.]

      proof

        assume

         A2: p in ( [.r, t.] \ ].s, t.]);

        then

         A3: not p in ].s, t.] by XBOOLE_0:def 5;

        

         A4: r <= p by A2, Th1;

        p <= s or t < p by A3, Th2;

        hence thesis by A2, A4, Th1;

      end;

      assume

       A5: p in [.r, s.];

      then

       A6: p <= s by Th1;

      

       A7: r <= p by A5, Th1;

      p <= t by A1, A6, XXREAL_0: 2;

      then

       A8: p in [.r, t.] by A7, Th1;

       not p in ].s, t.] by A6, Th2;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:193

    

     Th193: s < t implies ( ].r, t.] \ ].s, t.]) = ].r, s.]

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( ].r, t.] \ ].s, t.]) implies p in ].r, s.]

      proof

        assume

         A2: p in ( ].r, t.] \ ].s, t.]);

        then

         A3: not p in ].s, t.] by XBOOLE_0:def 5;

        

         A4: r < p by A2, Th2;

        p <= s or t < p by A3, Th2;

        hence thesis by A2, A4, Th2;

      end;

      assume

       A5: p in ].r, s.];

      then

       A6: p <= s by Th2;

      

       A7: r < p by A5, Th2;

      p <= t by A1, A6, XXREAL_0: 2;

      then

       A8: p in ].r, t.] by A7, Th2;

       not p in ].s, t.] by A6, Th2;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:194

    

     Th194: s < t implies ( [.r, t.[ \ [.s, t.[) = [.r, s.[

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( [.r, t.[ \ [.s, t.[) implies p in [.r, s.[

      proof

        assume

         A2: p in ( [.r, t.[ \ [.s, t.[);

        then

         A3: not p in [.s, t.[ by XBOOLE_0:def 5;

        

         A4: r <= p by A2, Th3;

        p < s or t <= p by A3, Th3;

        hence thesis by A2, A4, Th3;

      end;

      assume

       A5: p in [.r, s.[;

      then

       A6: p < s by Th3;

      

       A7: r <= p by A5, Th3;

      p < t by A1, A6, XXREAL_0: 2;

      then

       A8: p in [.r, t.[ by A7, Th3;

       not p in [.s, t.[ by A6, Th3;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:195

    

     Th195: s < t implies ( ].r, t.[ \ [.s, t.[) = ].r, s.[

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( ].r, t.[ \ [.s, t.[) implies p in ].r, s.[

      proof

        assume

         A2: p in ( ].r, t.[ \ [.s, t.[);

        then

         A3: not p in [.s, t.[ by XBOOLE_0:def 5;

        

         A4: r < p by A2, Th4;

        p < s or t <= p by A3, Th3;

        hence thesis by A2, A4, Th4;

      end;

      assume

       A5: p in ].r, s.[;

      then

       A6: p < s by Th4;

      

       A7: r < p by A5, Th4;

      p < t by A1, A6, XXREAL_0: 2;

      then

       A8: p in ].r, t.[ by A7, Th4;

       not p in [.s, t.[ by A6, Th3;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:196

    

     Th196: s < t implies ( [.r, t.[ \ ].s, t.[) = [.r, s.]

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( [.r, t.[ \ ].s, t.[) implies p in [.r, s.]

      proof

        assume

         A2: p in ( [.r, t.[ \ ].s, t.[);

        then

         A3: not p in ].s, t.[ by XBOOLE_0:def 5;

        

         A4: r <= p by A2, Th3;

        p <= s or t <= p by A3, Th4;

        hence thesis by A2, A4, Th1, Th3;

      end;

      assume

       A5: p in [.r, s.];

      then

       A6: p <= s by Th1;

      

       A7: r <= p by A5, Th1;

      p < t by A1, A6, XXREAL_0: 2;

      then

       A8: p in [.r, t.[ by A7, Th3;

       not p in ].s, t.[ by A6, Th4;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:197

    

     Th197: s < t implies ( ].r, t.[ \ ].s, t.[) = ].r, s.]

    proof

      assume that

       A1: s < t;

      let p;

      thus p in ( ].r, t.[ \ ].s, t.[) implies p in ].r, s.]

      proof

        assume

         A2: p in ( ].r, t.[ \ ].s, t.[);

        then

         A3: not p in ].s, t.[ by XBOOLE_0:def 5;

        

         A4: r < p by A2, Th4;

        p <= s or t <= p by A3, Th4;

        hence thesis by A2, A4, Th2, Th4;

      end;

      assume

       A5: p in ].r, s.];

      then

       A6: p <= s by Th2;

      

       A7: r < p by A5, Th2;

      p < t by A1, A6, XXREAL_0: 2;

      then

       A8: p in ].r, t.[ by A7, Th4;

       not p in ].s, t.[ by A6, Th4;

      hence thesis by A8, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:198

     [.p, q.[ meets [.r, s.[ implies ( [.p, q.[ \ [.r, s.[) = ( [.p, r.[ \/ [.s, q.[)

    proof

      assume [.p, q.[ meets [.r, s.[;

      then

      consider u such that

       A1: u in [.r, s.[ and

       A2: u in [.p, q.[;

      

       A3: r <= u by A1, Th3;

      

       A4: u <= s by A1, Th3;

      

       A5: p <= u by A2, Th3;

      u <= q by A2, Th3;

      then

       A6: r <= q by A3, XXREAL_0: 2;

      

       A7: p <= s by A4, A5, XXREAL_0: 2;

      let t;

      thus t in ( [.p, q.[ \ [.r, s.[) implies t in ( [.p, r.[ \/ [.s, q.[)

      proof

        assume

         A8: t in ( [.p, q.[ \ [.r, s.[);

        then

         A9: not t in [.r, s.[ by XBOOLE_0:def 5;

        

         A10: p <= t by A8, Th3;

        

         A11: t < q by A8, Th3;

        t < r or s <= t by A9, Th3;

        then t in [.p, r.[ or t in [.s, q.[ by A10, A11, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( [.p, r.[ \/ [.s, q.[);

      then t in [.p, r.[ or t in [.s, q.[ by XBOOLE_0:def 3;

      then

       A12: p <= t & t < r or s <= t & t < q by Th3;

      then

       A13: p <= t by A7, XXREAL_0: 2;

      t < q by A6, A12, XXREAL_0: 2;

      then

       A14: t in [.p, q.[ by A13, Th3;

       not t in [.r, s.[ by A12, Th3;

      hence thesis by A14, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:199

     ].p, q.] meets ].r, s.] implies ( ].p, q.] \ ].r, s.]) = ( ].p, r.] \/ ].s, q.])

    proof

      assume ].p, q.] meets ].r, s.];

      then

      consider u such that

       A1: u in ].r, s.] and

       A2: u in ].p, q.];

      

       A3: r < u by A1, Th2;

      

       A4: u <= s by A1, Th2;

      

       A5: p < u by A2, Th2;

      u <= q by A2, Th2;

      then

       A6: r <= q by A3, XXREAL_0: 2;

      

       A7: p <= s by A4, A5, XXREAL_0: 2;

      let t;

      thus t in ( ].p, q.] \ ].r, s.]) implies t in ( ].p, r.] \/ ].s, q.])

      proof

        assume

         A8: t in ( ].p, q.] \ ].r, s.]);

        then

         A9: not t in ].r, s.] by XBOOLE_0:def 5;

        

         A10: p < t by A8, Th2;

        

         A11: t <= q by A8, Th2;

        t <= r or s < t by A9, Th2;

        then t in ].p, r.] or t in ].s, q.] by A10, A11, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume t in ( ].p, r.] \/ ].s, q.]);

      then t in ].p, r.] or t in ].s, q.] by XBOOLE_0:def 3;

      then

       A12: p < t & t <= r or s < t & t <= q by Th2;

      then

       A13: p < t by A7, XXREAL_0: 2;

      t <= q by A6, A12, XXREAL_0: 2;

      then

       A14: t in ].p, q.] by A13, Th2;

       not t in ].r, s.] by A12, Th2;

      hence thesis by A14, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:200

    p <= r & s <= q implies ( [.p, q.] \ ( [.p, r.] \/ [.s, q.])) = ].r, s.[

    proof

      assume that

       A1: p <= r and

       A2: s <= q;

      

      thus ( [.p, q.] \ ( [.p, r.] \/ [.s, q.])) = (( [.p, q.] \ [.p, r.]) \ [.s, q.]) by XBOOLE_1: 41

      .= ( ].r, q.] \ [.s, q.]) by A1, Th182

      .= ].r, s.[ by A2, Th191;

    end;

    theorem :: XXREAL_1:201

    r <= s & s <= t implies ( [.r, t.] \ {s}) = ( [.r, s.[ \/ ].s, t.])

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      let p;

      thus p in ( [.r, t.] \ {s}) implies p in ( [.r, s.[ \/ ].s, t.])

      proof

        assume

         A3: p in ( [.r, t.] \ {s});

        then not p in {s} by XBOOLE_0:def 5;

        then p <> s by TARSKI:def 1;

        then r <= p & p < s or s < p & p <= t by A3, Th1, XXREAL_0: 1;

        then p in [.r, s.[ or p in ].s, t.] by Th2, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume p in ( [.r, s.[ \/ ].s, t.]);

      then p in [.r, s.[ or p in ].s, t.] by XBOOLE_0:def 3;

      then

       A4: r <= p & p < s or s < p & p <= t by Th2, Th3;

      then

       A5: r <= p by A1, XXREAL_0: 2;

      p <= t by A2, A4, XXREAL_0: 2;

      then

       A6: p in [.r, t.] by A5, Th1;

       not p in {s} by A4, TARSKI:def 1;

      hence thesis by A6, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:202

    r <= s & s < t implies ( [.r, t.[ \ {s}) = ( [.r, s.[ \/ ].s, t.[)

    proof

      assume that

       A1: r <= s and

       A2: s < t;

      let p;

      thus p in ( [.r, t.[ \ {s}) implies p in ( [.r, s.[ \/ ].s, t.[)

      proof

        assume

         A3: p in ( [.r, t.[ \ {s});

        then not p in {s} by XBOOLE_0:def 5;

        then p <> s by TARSKI:def 1;

        then r <= p & p < s or s < p & p < t by A3, Th3, XXREAL_0: 1;

        then p in [.r, s.[ or p in ].s, t.[ by Th3, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume p in ( [.r, s.[ \/ ].s, t.[);

      then p in [.r, s.[ or p in ].s, t.[ by XBOOLE_0:def 3;

      then

       A4: r <= p & p < s or s < p & p < t by Th3, Th4;

      then

       A5: r <= p by A1, XXREAL_0: 2;

      p < t by A2, A4, XXREAL_0: 2;

      then

       A6: p in [.r, t.[ by A5, Th3;

       not p in {s} by A4, TARSKI:def 1;

      hence thesis by A6, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:203

    r < s & s <= t implies ( ].r, t.] \ {s}) = ( ].r, s.[ \/ ].s, t.])

    proof

      assume that

       A1: r < s and

       A2: s <= t;

      let p;

      thus p in ( ].r, t.] \ {s}) implies p in ( ].r, s.[ \/ ].s, t.])

      proof

        assume

         A3: p in ( ].r, t.] \ {s});

        then not p in {s} by XBOOLE_0:def 5;

        then p <> s by TARSKI:def 1;

        then r < p & p < s or s < p & p <= t by A3, Th2, XXREAL_0: 1;

        then p in ].r, s.[ or p in ].s, t.] by Th2, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume p in ( ].r, s.[ \/ ].s, t.]);

      then p in ].r, s.[ or p in ].s, t.] by XBOOLE_0:def 3;

      then

       A4: r < p & p < s or s < p & p <= t by Th2, Th4;

      then

       A5: r < p by A1, XXREAL_0: 2;

      p <= t by A2, A4, XXREAL_0: 2;

      then

       A6: p in ].r, t.] by A5, Th2;

       not p in {s} by A4, TARSKI:def 1;

      hence thesis by A6, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:204

    r < s & s < t implies ( ].r, t.[ \ {s}) = ( ].r, s.[ \/ ].s, t.[)

    proof

      assume that

       A1: r < s and

       A2: s < t;

      let p;

      thus p in ( ].r, t.[ \ {s}) implies p in ( ].r, s.[ \/ ].s, t.[)

      proof

        assume

         A3: p in ( ].r, t.[ \ {s});

        then not p in {s} by XBOOLE_0:def 5;

        then p <> s by TARSKI:def 1;

        then r < p & p < s or s < p & p < t by A3, Th4, XXREAL_0: 1;

        then p in ].r, s.[ or p in ].s, t.[ by Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume p in ( ].r, s.[ \/ ].s, t.[);

      then p in ].r, s.[ or p in ].s, t.[ by XBOOLE_0:def 3;

      then

       A4: r < p & p < s or s < p & p < t by Th4;

      then

       A5: r < p by A1, XXREAL_0: 2;

      p < t by A2, A4, XXREAL_0: 2;

      then

       A6: p in ].r, t.[ by A5, Th4;

       not p in {s} by A4, TARSKI:def 1;

      hence thesis by A6, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:205

     not s in ( ].r, s.[ \/ ].s, t.[)

    proof

      assume s in ( ].r, s.[ \/ ].s, t.[);

      then s in ].r, s.[ or s in ].s, t.[ by XBOOLE_0:def 3;

      hence contradiction by Th4;

    end;

    theorem :: XXREAL_1:206

     not s in ( [.r, s.[ \/ ].s, t.[)

    proof

      assume s in ( [.r, s.[ \/ ].s, t.[);

      then s in [.r, s.[ or s in ].s, t.[ by XBOOLE_0:def 3;

      hence contradiction by Th3, Th4;

    end;

    theorem :: XXREAL_1:207

     not s in ( ].r, s.[ \/ ].s, t.])

    proof

      assume s in ( ].r, s.[ \/ ].s, t.]);

      then s in ].r, s.[ or s in ].s, t.] by XBOOLE_0:def 3;

      hence contradiction by Th2, Th4;

    end;

    theorem :: XXREAL_1:208

     not s in ( [.r, s.[ \/ ].s, t.])

    proof

      assume s in ( [.r, s.[ \/ ].s, t.]);

      then s in [.r, s.[ or s in ].s, t.] by XBOOLE_0:def 3;

      hence contradiction by Th2, Th3;

    end;

    begin

    theorem :: XXREAL_1:209

     [. -infty , +infty .] = ExtREAL

    proof

      let r;

      thus r in [. -infty , +infty .] implies r in ExtREAL by XXREAL_0:def 1;

      assume r in ExtREAL ;

      

       A1: -infty <= r by XXREAL_0: 5;

      r <= +infty by XXREAL_0: 3;

      hence thesis by A1, Th1;

    end;

    theorem :: XXREAL_1:210

     ].p, -infty .[ = {}

    proof

       not ex x be object st x in ].p, -infty .[

      proof

        given x be object such that

         A1: x in ].p, -infty .[;

        reconsider s = x as ExtReal by A1;

        s < -infty by A1, Th4;

        hence contradiction by XXREAL_0: 5;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:211

     [.p, -infty .[ = {}

    proof

       not ex x be object st x in [.p, -infty .[

      proof

        given x be object such that

         A1: x in [.p, -infty .[;

        reconsider s = x as ExtReal by A1;

        s < -infty by A1, Th3;

        hence contradiction by XXREAL_0: 5;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:212

     ].p, -infty .] = {}

    proof

       not ex x be object st x in ].p, -infty .]

      proof

        given x be object such that

         A1: x in ].p, -infty .];

        reconsider s = x as ExtReal by A1;

        

         A2: p < s by A1, Th2;

        s <= -infty by A1, Th2;

        then p < -infty by A2, XXREAL_0: 2;

        hence contradiction by XXREAL_0: 5;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:213

    p <> -infty implies [.p, -infty .] = {}

    proof

      assume

       A1: p <> -infty ;

       not ex x be object st x in [.p, -infty .]

      proof

        given x be object such that

         A2: x in [.p, -infty .];

        reconsider s = x as ExtReal by A2;

        

         A3: p <= s by A2, Th1;

        s <= -infty by A2, Th1;

        hence contradiction by A1, A3, XXREAL_0: 2, XXREAL_0: 6;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:214

     ]. +infty , p.[ = {}

    proof

       not ex x be object st x in ]. +infty , p.[

      proof

        given x be object such that

         A1: x in ]. +infty , p.[;

        reconsider s = x as ExtReal by A1;

         +infty < s by A1, Th4;

        hence contradiction by XXREAL_0: 3;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:215

     [. +infty , p.[ = {}

    proof

       not ex x be object st x in [. +infty , p.[

      proof

        given x be object such that

         A1: x in [. +infty , p.[;

        reconsider s = x as ExtReal by A1;

        

         A2: +infty <= s by A1, Th3;

        s < p by A1, Th3;

        then p > +infty by A2, XXREAL_0: 2;

        hence contradiction by XXREAL_0: 3;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:216

     ]. +infty , p.] = {}

    proof

       not ex x be object st x in ]. +infty , p.]

      proof

        given x be object such that

         A1: x in ]. +infty , p.];

        reconsider s = x as ExtReal by A1;

         +infty < s by A1, Th2;

        hence contradiction by XXREAL_0: 3;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:217

    p <> +infty implies [. +infty , p.] = {}

    proof

      assume

       A1: p <> +infty ;

       not ex x be object st x in [. +infty , p.]

      proof

        given x be object such that

         A2: x in [. +infty , p.];

        reconsider s = x as ExtReal by A2;

        

         A3: +infty <= s by A2, Th1;

        s <= p by A2, Th1;

        hence contradiction by A1, A3, XXREAL_0: 2, XXREAL_0: 4;

      end;

      hence thesis;

    end;

    theorem :: XXREAL_1:218

    p > q implies p in ].q, +infty .] by XXREAL_0: 3, Th2;

    theorem :: XXREAL_1:219

    q <= p implies p in [.q, +infty .]

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:220

    p <= q implies p in [. -infty , q.]

    proof

      p >= -infty by XXREAL_0: 5;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:221

    p < q implies p in [. -infty , q.[ by XXREAL_0: 5, Th3;

    begin

    theorem :: XXREAL_1:222

    p <= q implies [.p, q.] = ( [.p, q.] \/ [.q, p.])

    proof

      assume

       A1: p <= q;

      then

       A2: [.q, p.] c= {p} by Th85;

      p in [.p, q.] by A1, Th1;

      then {p} c= [.p, q.] by ZFMISC_1: 31;

      hence thesis by A2, XBOOLE_1: 1, XBOOLE_1: 12;

    end;

    theorem :: XXREAL_1:223

    r <= s & s <= t implies not r in ( ].s, t.[ \/ ].t, p.[)

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      assume r in ( ].s, t.[ \/ ].t, p.[);

      then r in ].s, t.[ or r in ].t, p.[ by XBOOLE_0:def 3;

      then s < r & r < t or t < r & r < p by Th4;

      hence contradiction by A1, A2, XXREAL_0: 2;

    end;

    theorem :: XXREAL_1:224

    

     Th224: REAL = ]. -infty , +infty .[

    proof

      let x be ExtReal;

      thus x in REAL implies x in ]. -infty , +infty .[

      proof

        assume

         A1: x in REAL ;

        then

         A2: -infty < x by XXREAL_0: 12;

        x < +infty by A1, XXREAL_0: 9;

        hence thesis by A2, Th4;

      end;

      assume

       A3: x in ]. -infty , +infty .[;

      then

       A4: -infty < x by Th4;

      x < +infty by A3, Th4;

      hence thesis by A4, XXREAL_0: 14;

    end;

    theorem :: XXREAL_1:225

    

     Th225: ].p, q.[ c= REAL

    proof

      let x be ExtReal;

      assume

       A1: x in ].p, q.[;

      then

       A2: p < x by Th4;

      x < q by A1, Th4;

      hence thesis by A2, XXREAL_0: 48;

    end;

    theorem :: XXREAL_1:226

    

     Th226: p in REAL implies [.p, q.[ c= REAL

    proof

      assume

       A1: p in REAL ;

      let x be ExtReal;

      assume

       A2: x in [.p, q.[;

      then

       A3: p <= x by Th3;

      x < q by A2, Th3;

      hence thesis by A1, A3, XXREAL_0: 46;

    end;

    theorem :: XXREAL_1:227

    

     Th227: q in REAL implies ].p, q.] c= REAL

    proof

      assume

       A1: q in REAL ;

      let x be ExtReal;

      assume

       A2: x in ].p, q.];

      then

       A3: p < x by Th2;

      x <= q by A2, Th2;

      hence thesis by A1, A3, XXREAL_0: 47;

    end;

    theorem :: XXREAL_1:228

    

     Th228: p in REAL & q in REAL implies [.p, q.] c= REAL

    proof

      assume that

       A1: p in REAL and

       A2: q in REAL ;

      let x be ExtReal;

      assume

       A3: x in [.p, q.];

      then

       A4: p <= x by Th1;

      x <= q by A3, Th1;

      hence thesis by A1, A2, A4, XXREAL_0: 45;

    end;

    registration

      let p, q;

      cluster ].p, q.[ -> real-membered;

      coherence by Th225, MEMBERED: 21;

    end

    registration

      let p be Real, q;

      cluster [.p, q.[ -> real-membered;

      coherence

      proof

        p in REAL by XREAL_0:def 1;

        then [.p, q.[ c= REAL by Th226;

        hence thesis;

      end;

    end

    registration

      let q be Real, p;

      cluster ].p, q.] -> real-membered;

      coherence

      proof

        q in REAL by XREAL_0:def 1;

        then ].p, q.] c= REAL by Th227;

        hence thesis;

      end;

    end

    registration

      let p,q be Real;

      cluster [.p, q.] -> real-membered;

      coherence

      proof

        

         A1: p in REAL by XREAL_0:def 1;

        q in REAL by XREAL_0:def 1;

        then [.p, q.] c= REAL by A1, Th228;

        hence thesis;

      end;

    end

    theorem :: XXREAL_1:229

     ]. -infty , s.[ = { g : g < s }

    proof

      thus ]. -infty , s.[ c= { g : g < s }

      proof

        let x be Real;

        assume

         A1: x in ]. -infty , s.[;

        

         A2: x < s by A1, Th4;

        thus thesis by A2;

      end;

      let x be object;

      assume x in { g : g < s };

      then

      consider g such that

       A3: x = g and

       A4: g < s;

      g in REAL by XREAL_0:def 1;

      then -infty < g by XXREAL_0: 12;

      hence thesis by A3, A4, Th4;

    end;

    theorem :: XXREAL_1:230

     ].s, +infty .[ = { g : s < g }

    proof

      thus ].s, +infty .[ c= { g : s < g }

      proof

        let x be Real;

        assume x in ].s, +infty .[;

        then

         A1: s < x by Th4;

        thus thesis by A1;

      end;

      let x be object;

      assume x in { g : s < g };

      then

      consider g such that

       A2: x = g and

       A3: s < g;

      g in REAL by XREAL_0:def 1;

      then g < +infty by XXREAL_0: 9;

      hence thesis by A2, A3, Th4;

    end;

    theorem :: XXREAL_1:231

    for s be Real holds ]. -infty , s.] = { g : g <= s }

    proof

      let s be Real;

      thus ]. -infty , s.] c= { g : g <= s }

      proof

        let x be Real;

        assume x in ]. -infty , s.];

        then

         A1: x <= s by Th2;

        thus thesis by A1;

      end;

      let x be object;

      assume x in { g : g <= s };

      then

      consider g such that

       A2: x = g and

       A3: g <= s;

      g in REAL by XREAL_0:def 1;

      then -infty < g by XXREAL_0: 12;

      hence thesis by A2, A3, Th2;

    end;

    theorem :: XXREAL_1:232

    for s be Real holds [.s, +infty .[ = { g : s <= g }

    proof

      let s be Real;

      thus [.s, +infty .[ c= { g : s <= g }

      proof

        let x be Real;

        assume x in [.s, +infty .[;

        then

         A1: s <= x by Th3;

        thus thesis by A1;

      end;

      let x be object;

      assume x in { g : s <= g };

      then

      consider g such that

       A2: x = g and

       A3: s <= g;

      g in REAL by XREAL_0:def 1;

      then g < +infty by XXREAL_0: 9;

      hence thesis by A2, A3, Th3;

    end;

    theorem :: XXREAL_1:233

    for x be Real holds x in ]. -infty , u.[ iff x < u

    proof

      let x be Real;

      x in REAL by XREAL_0:def 1;

      then -infty < x by XXREAL_0: 12;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:234

    for x be Real holds x in ]. -infty , u.] iff x <= u

    proof

      let x be Real;

      x in REAL by XREAL_0:def 1;

      then -infty < x by XXREAL_0: 12;

      hence thesis by Th2;

    end;

    theorem :: XXREAL_1:235

    for x be Real holds x in ].u, +infty .[ iff u < x

    proof

      let x be Real;

      x in REAL by XREAL_0:def 1;

      then x < +infty by XXREAL_0: 9;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:236

    for x be Real holds x in [.u, +infty .[ iff u <= x

    proof

      let x be Real;

      x in REAL by XREAL_0:def 1;

      then x < +infty by XXREAL_0: 9;

      hence thesis by Th3;

    end;

    theorem :: XXREAL_1:237

    p <= r implies [.r, s.] c= [.p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th34;

    end;

    theorem :: XXREAL_1:238

    p <= r implies [.r, s.[ c= [.p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th35;

    end;

    theorem :: XXREAL_1:239

    p <= r implies ].r, s.] c= [.p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th36;

    end;

    theorem :: XXREAL_1:240

    p <= r implies ].r, s.[ c= [.p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th37;

    end;

    theorem :: XXREAL_1:241

    p <= r implies [.r, s.[ c= [.p, +infty .[

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th38;

    end;

    theorem :: XXREAL_1:242

    p < r implies [.r, s.] c= ].p, +infty .] by Th39, XXREAL_0: 3;

    theorem :: XXREAL_1:243

    p < r implies [.r, s.[ c= ].p, +infty .] by Th40, XXREAL_0: 3;

    theorem :: XXREAL_1:244

    p <= r implies ].r, s.[ c= ].p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th41;

    end;

    theorem :: XXREAL_1:245

    p <= r implies ].r, s.] c= ].p, +infty .]

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th42;

    end;

    theorem :: XXREAL_1:246

    p <= r implies ].r, s.[ c= [.p, +infty .[

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th45;

    end;

    theorem :: XXREAL_1:247

    p <= r implies ].r, s.[ c= ].p, +infty .[

    proof

      s <= +infty by XXREAL_0: 3;

      hence thesis by Th46;

    end;

    theorem :: XXREAL_1:248

    p < r implies [.r, s.[ c= ].p, +infty .[ by Th48, XXREAL_0: 3;

    theorem :: XXREAL_1:249

    for s be Real st p < r holds [.r, s.] c= ].p, +infty .[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      then s < +infty by XXREAL_0: 9;

      hence thesis by Th47;

    end;

    theorem :: XXREAL_1:250

    for s be Real st p <= r holds ].r, s.] c= ].p, +infty .[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th49, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:251

    for s be Real st p <= r holds [.r, s.] c= [.p, +infty .[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th43, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:252

    for s be Real st p <= r holds ].r, s.] c= [.p, +infty .[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th44, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:253

    s <= q implies [.r, s.] c= [. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th34;

    end;

    theorem :: XXREAL_1:254

    s <= q implies [.r, s.[ c= [. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th35;

    end;

    theorem :: XXREAL_1:255

    s <= q implies ].r, s.] c= [. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th36;

    end;

    theorem :: XXREAL_1:256

    s <= q implies ].r, s.[ c= [. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th37;

    end;

    theorem :: XXREAL_1:257

    s <= q implies [.r, s.[ c= [. -infty , q.[

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th38;

    end;

    theorem :: XXREAL_1:258

    s <= q implies ].r, s.[ c= ]. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th41;

    end;

    theorem :: XXREAL_1:259

    s <= q implies ].r, s.] c= ]. -infty , q.]

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th42;

    end;

    theorem :: XXREAL_1:260

    s < q implies [.r, s.] c= [. -infty , q.[ by Th43, XXREAL_0: 5;

    theorem :: XXREAL_1:261

    s < q implies ].r, s.] c= [. -infty , q.[ by Th44, XXREAL_0: 5;

    theorem :: XXREAL_1:262

    s <= q implies ].r, s.[ c= [. -infty , q.[

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th45;

    end;

    theorem :: XXREAL_1:263

    s <= q implies ].r, s.[ c= ]. -infty , q.[

    proof

       -infty <= r by XXREAL_0: 5;

      hence thesis by Th46;

    end;

    theorem :: XXREAL_1:264

    s < q implies ].r, s.] c= ]. -infty , q.[ by Th49, XXREAL_0: 5;

    theorem :: XXREAL_1:265

    for r be Real st s <= q holds [.r, s.] c= ]. -infty , q.]

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      hence thesis by Th39, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:266

    for r be Real st s <= q holds [.r, s.[ c= ]. -infty , q.]

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      hence thesis by Th40, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:267

    for r be Real st s < q holds [.r, s.] c= ]. -infty , q.[

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      then -infty < r by XXREAL_0: 12;

      hence thesis by Th47;

    end;

    theorem :: XXREAL_1:268

    for r be Real st s <= q holds [.r, s.[ c= ]. -infty , q.[

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      hence thesis by Th48, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:269

    for a,b be ExtReal holds ( ]. -infty , b.[ /\ ].a, +infty .[) = ].a, b.[

    proof

      let a,b be ExtReal;

      

       A1: -infty <= a by XXREAL_0: 5;

      b <= +infty by XXREAL_0: 3;

      hence thesis by A1, Th160;

    end;

    theorem :: XXREAL_1:270

    for b be Real holds ( ]. -infty , b.] /\ ].p, +infty .[) = ].p, b.]

    proof

      let b be Real;

      

       A1: b in REAL by XREAL_0:def 1;

       -infty <= p by XXREAL_0: 5;

      hence thesis by A1, Th159, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:271

    for a be Real holds ( ]. -infty , p.[ /\ [.a, +infty .[) = [.a, p.[

    proof

      let a be Real;

      a in REAL by XREAL_0:def 1;

      then -infty < a by XXREAL_0: 12;

      hence thesis by Th154, XXREAL_0: 3;

    end;

    theorem :: XXREAL_1:272

    for a,b be Real holds ( ]. -infty , a.] /\ [.b, +infty .[) = [.b, a.]

    proof

      let a,b be Real;

      

       A1: a in REAL by XREAL_0:def 1;

      b in REAL by XREAL_0:def 1;

      then

       A2: -infty < b by XXREAL_0: 12;

      a < +infty by A1, XXREAL_0: 9;

      hence thesis by A2, Th152;

    end;

    theorem :: XXREAL_1:273

    s <= p implies [.r, s.[ misses ].p, q.[

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.[;

      then t <= s by Th3;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:274

    s <= p implies [.r, s.[ misses ].p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in [.r, s.[;

      then t <= s by Th3;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th2;

    end;

    theorem :: XXREAL_1:275

    s <= p implies ].r, s.[ misses ].p, q.[

    proof

      assume

       A1: s <= p;

      let t be Real;

      assume t in ].r, s.[;

      then t <= s by Th4;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th4;

    end;

    theorem :: XXREAL_1:276

    s <= p implies ].r, s.[ misses ].p, q.]

    proof

      assume

       A1: s <= p;

      let t;

      assume t in ].r, s.[;

      then t <= s by Th4;

      then t <= p by A1, XXREAL_0: 2;

      hence thesis by Th2;

    end;

    theorem :: XXREAL_1:277

    s < p implies [.r, s.] misses [.p, q.[

    proof

      assume

       A1: s < p;

      let t;

      assume t in [.r, s.];

      then t <= s by Th1;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th3;

    end;

    theorem :: XXREAL_1:278

    s < p implies [.r, s.] misses [.p, q.]

    proof

      assume

       A1: s < p;

      let t;

      assume t in [.r, s.];

      then t <= s by Th1;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:279

    s < p implies ].r, s.] misses [.p, q.[

    proof

      assume

       A1: s < p;

      let t;

      assume t in ].r, s.];

      then t <= s by Th2;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th3;

    end;

    theorem :: XXREAL_1:280

    s < p implies ].r, s.] misses [.p, q.]

    proof

      assume

       A1: s < p;

      let t;

      assume t in ].r, s.];

      then t <= s by Th2;

      then t < p by A1, XXREAL_0: 2;

      hence thesis by Th1;

    end;

    theorem :: XXREAL_1:281

    ( [. -infty , t.] \ [. -infty , s.]) = ].s, t.] by Th182, XXREAL_0: 5;

    theorem :: XXREAL_1:282

    ( [. -infty , t.[ \ [. -infty , s.]) = ].s, t.[ by Th183, XXREAL_0: 5;

    theorem :: XXREAL_1:283

    ( [. -infty , t.] \ [. -infty , s.]) = ].s, t.] by Th186, XXREAL_0: 5;

    theorem :: XXREAL_1:284

    ( [.r, +infty .] \ [.s, +infty .]) = [.r, s.[ by Th190, XXREAL_0: 3;

    theorem :: XXREAL_1:285

    ( ].r, +infty .] \ [.s, +infty .]) = ].r, s.[ by Th191, XXREAL_0: 3;

    theorem :: XXREAL_1:286

    for s be Real holds ( [. -infty , t.] \ [. -infty , s.[) = [.s, t.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th184, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:287

    for s be Real holds ( [. -infty , t.[ \ [. -infty , s.[) = [.s, t.[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th185, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:288

    for s be Real holds ( ]. -infty , t.[ \ ]. -infty , s.]) = ].s, t.[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th187, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:289

    for s be Real holds ( ]. -infty , t.] \ ]. -infty , s.[) = [.s, t.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th188, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:290

    for s be Real holds ( ]. -infty , t.[ \ ]. -infty , s.[) = [.s, t.[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th189, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:291

    for s be Real holds ( [.r, +infty .] \ ].s, +infty .]) = [.r, s.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th192, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:292

    for s be Real holds ( ].r, +infty .] \ ].s, +infty .]) = ].r, s.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th193, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:293

    for s be Real holds ( [.r, +infty .[ \ [.s, +infty .[) = [.r, s.[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th194, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:294

    for s be Real holds ( ].r, +infty .[ \ [.s, +infty .[) = ].r, s.[

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th195, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:295

    for s be Real holds ( [.r, +infty .[ \ ].s, +infty .[) = [.r, s.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th196, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:296

    for s be Real holds ( ].r, +infty .[ \ ].s, +infty .[) = ].r, s.]

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th197, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:297

    

     Th297: r < s & p < q implies ( ].r, q.[ \ ].p, s.[) = ( ].r, p.] \/ [.s, q.[)

    proof

      assume that

       A1: r < s and

       A2: p < q;

      let x be ExtReal;

      thus x in ( ].r, q.[ \ ].p, s.[) implies x in ( ].r, p.] \/ [.s, q.[)

      proof

        assume

         A3: x in ( ].r, q.[ \ ].p, s.[);

        then

         A4: not x in ].p, s.[ by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th4;

        

         A6: x < q by A3, Th4;

         not (p < x & x < s) by A4, Th4;

        then x in ].r, p.] or x in [.s, q.[ by A5, A6, Th2, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.] \/ [.s, q.[);

      then x in ].r, p.] or x in [.s, q.[ by XBOOLE_0:def 3;

      then

       A7: r < x & x <= p or s <= x & x < q by Th2, Th3;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.[ by A8, Th4;

       not x in ].p, s.[ by A7, Th4;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:298

    

     Th298: r <= s & p < q implies ( [.r, q.[ \ ].p, s.[) = ( [.r, p.] \/ [.s, q.[)

    proof

      assume that

       A1: r <= s and

       A2: p < q;

      let x be ExtReal;

      thus x in ( [.r, q.[ \ ].p, s.[) implies x in ( [.r, p.] \/ [.s, q.[)

      proof

        assume

         A3: x in ( [.r, q.[ \ ].p, s.[);

        then

         A4: not x in ].p, s.[ by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th3;

        

         A6: x < q by A3, Th3;

         not (p < x & x < s) by A4, Th4;

        then x in [.r, p.] or x in [.s, q.[ by A5, A6, Th1, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.] \/ [.s, q.[);

      then x in [.r, p.] or x in [.s, q.[ by XBOOLE_0:def 3;

      then

       A7: r <= x & x <= p or s <= x & x < q by Th1, Th3;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.[ by A8, Th3;

       not x in ].p, s.[ by A7, Th4;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:299

    

     Th299: r < s & p <= q implies ( ].r, q.] \ ].p, s.[) = ( ].r, p.] \/ [.s, q.])

    proof

      assume that

       A1: r < s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( ].r, q.] \ ].p, s.[) implies x in ( ].r, p.] \/ [.s, q.])

      proof

        assume

         A3: x in ( ].r, q.] \ ].p, s.[);

        then

         A4: not x in ].p, s.[ by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th2;

        

         A6: x <= q by A3, Th2;

         not (p < x & x < s) by A4, Th4;

        then x in ].r, p.] or x in [.s, q.] by A5, A6, Th1, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.] \/ [.s, q.]);

      then x in ].r, p.] or x in [.s, q.] by XBOOLE_0:def 3;

      then

       A7: r < x & x <= p or s <= x & x <= q by Th1, Th2;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.] by A8, Th2;

       not x in ].p, s.[ by A7, Th4;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:300

    

     Th300: r <= s & p <= q implies ( [.r, q.] \ ].p, s.[) = ( [.r, p.] \/ [.s, q.])

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.] \ ].p, s.[) implies x in ( [.r, p.] \/ [.s, q.])

      proof

        assume

         A3: x in ( [.r, q.] \ ].p, s.[);

        then

         A4: not x in ].p, s.[ by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th1;

        

         A6: x <= q by A3, Th1;

         not (p < x & x < s) by A4, Th4;

        then x in [.r, p.] or x in [.s, q.] by A5, A6, Th1;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.] \/ [.s, q.]);

      then x in [.r, p.] or x in [.s, q.] by XBOOLE_0:def 3;

      then

       A7: r <= x & x <= p or s <= x & x <= q by Th1;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.] by A8, Th1;

       not x in ].p, s.[ by A7, Th4;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:301

    

     Th301: r < s & p <= q implies ( ].r, q.[ \ [.p, s.[) = ( ].r, p.[ \/ [.s, q.[)

    proof

      assume that

       A1: r < s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( ].r, q.[ \ [.p, s.[) implies x in ( ].r, p.[ \/ [.s, q.[)

      proof

        assume

         A3: x in ( ].r, q.[ \ [.p, s.[);

        then

         A4: not x in [.p, s.[ by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th4;

        

         A6: x < q by A3, Th4;

         not (p <= x & x < s) by A4, Th3;

        then x in ].r, p.[ or x in [.s, q.[ by A5, A6, Th3, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.[ \/ [.s, q.[);

      then x in ].r, p.[ or x in [.s, q.[ by XBOOLE_0:def 3;

      then

       A7: r < x & x < p or s <= x & x < q by Th3, Th4;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.[ by A8, Th4;

       not x in [.p, s.[ by A7, Th3;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:302

    

     Th302: r <= s & p <= q implies ( [.r, q.[ \ [.p, s.[) = ( [.r, p.[ \/ [.s, q.[)

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.[ \ [.p, s.[) implies x in ( [.r, p.[ \/ [.s, q.[)

      proof

        assume

         A3: x in ( [.r, q.[ \ [.p, s.[);

        then

         A4: not x in [.p, s.[ by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th3;

        

         A6: x < q by A3, Th3;

         not (p <= x & x < s) by A4, Th3;

        then x in [.r, p.[ or x in [.s, q.[ by A5, A6, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.[ \/ [.s, q.[);

      then x in [.r, p.[ or x in [.s, q.[ by XBOOLE_0:def 3;

      then

       A7: r <= x & x < p or s <= x & x < q by Th3;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.[ by A8, Th3;

       not x in [.p, s.[ by A7, Th3;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:303

    

     Th303: r < s & p <= q implies ( ].r, q.] \ [.p, s.[) = ( ].r, p.[ \/ [.s, q.])

    proof

      assume that

       A1: r < s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( ].r, q.] \ [.p, s.[) implies x in ( ].r, p.[ \/ [.s, q.])

      proof

        assume

         A3: x in ( ].r, q.] \ [.p, s.[);

        then

         A4: not x in [.p, s.[ by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th2;

        

         A6: x <= q by A3, Th2;

         not (p <= x & x < s) by A4, Th3;

        then x in ].r, p.[ or x in [.s, q.] by A5, A6, Th1, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.[ \/ [.s, q.]);

      then x in ].r, p.[ or x in [.s, q.] by XBOOLE_0:def 3;

      then

       A7: r < x & x < p or s <= x & x <= q by Th1, Th4;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.] by A8, Th2;

       not x in [.p, s.[ by A7, Th3;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:304

    

     Th304: r <= s & p <= q implies ( [.r, q.] \ [.p, s.[) = ( [.r, p.[ \/ [.s, q.])

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.] \ [.p, s.[) implies x in ( [.r, p.[ \/ [.s, q.])

      proof

        assume

         A3: x in ( [.r, q.] \ [.p, s.[);

        then

         A4: not x in [.p, s.[ by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th1;

        

         A6: x <= q by A3, Th1;

         not (p <= x & x < s) by A4, Th3;

        then x in [.r, p.[ or x in [.s, q.] by A5, A6, Th1, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.[ \/ [.s, q.]);

      then x in [.r, p.[ or x in [.s, q.] by XBOOLE_0:def 3;

      then

       A7: r <= x & x < p or s <= x & x <= q by Th1, Th3;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.] by A8, Th1;

       not x in [.p, s.[ by A7, Th3;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:305

    

     Th305: r < s & p < q implies ( ].r, q.[ \ ].p, s.]) = ( ].r, p.] \/ ].s, q.[)

    proof

      assume that

       A1: r < s and

       A2: p < q;

      let x be ExtReal;

      thus x in ( ].r, q.[ \ ].p, s.]) implies x in ( ].r, p.] \/ ].s, q.[)

      proof

        assume

         A3: x in ( ].r, q.[ \ ].p, s.]);

        then

         A4: not x in ].p, s.] by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th4;

        

         A6: x < q by A3, Th4;

         not (p < x & x <= s) by A4, Th2;

        then x in ].r, p.] or x in ].s, q.[ by A5, A6, Th2, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.] \/ ].s, q.[);

      then x in ].r, p.] or x in ].s, q.[ by XBOOLE_0:def 3;

      then

       A7: r < x & x <= p or s < x & x < q by Th2, Th4;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.[ by A8, Th4;

       not x in ].p, s.] by A7, Th2;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:306

    

     Th306: r <= s & p < q implies ( [.r, q.[ \ ].p, s.]) = ( [.r, p.] \/ ].s, q.[)

    proof

      assume that

       A1: r <= s and

       A2: p < q;

      let x be ExtReal;

      thus x in ( [.r, q.[ \ ].p, s.]) implies x in ( [.r, p.] \/ ].s, q.[)

      proof

        assume

         A3: x in ( [.r, q.[ \ ].p, s.]);

        then

         A4: not x in ].p, s.] by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th3;

        

         A6: x < q by A3, Th3;

         not (p < x & x <= s) by A4, Th2;

        then x in [.r, p.] or x in ].s, q.[ by A5, A6, Th1, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.] \/ ].s, q.[);

      then x in [.r, p.] or x in ].s, q.[ by XBOOLE_0:def 3;

      then

       A7: r <= x & x <= p or s < x & x < q by Th1, Th4;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.[ by A8, Th3;

       not x in ].p, s.] by A7, Th2;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:307

    

     Th307: r < s & p <= q implies ( ].r, q.] \ ].p, s.]) = ( ].r, p.] \/ ].s, q.])

    proof

      assume that

       A1: r < s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( ].r, q.] \ ].p, s.]) implies x in ( ].r, p.] \/ ].s, q.])

      proof

        assume

         A3: x in ( ].r, q.] \ ].p, s.]);

        then

         A4: not x in ].p, s.] by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th2;

        

         A6: x <= q by A3, Th2;

         not (p < x & x <= s) by A4, Th2;

        then x in ].r, p.] or x in ].s, q.] by A5, A6, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.] \/ ].s, q.]);

      then x in ].r, p.] or x in ].s, q.] by XBOOLE_0:def 3;

      then

       A7: r < x & x <= p or s < x & x <= q by Th2;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.] by A8, Th2;

       not x in ].p, s.] by A7, Th2;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:308

    

     Th308: r <= s & p <= q implies ( [.r, q.] \ ].p, s.]) = ( [.r, p.] \/ ].s, q.])

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.] \ ].p, s.]) implies x in ( [.r, p.] \/ ].s, q.])

      proof

        assume

         A3: x in ( [.r, q.] \ ].p, s.]);

        then

         A4: not x in ].p, s.] by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th1;

        

         A6: x <= q by A3, Th1;

         not (p < x & x <= s) by A4, Th2;

        then x in [.r, p.] or x in ].s, q.] by A5, A6, Th1, Th2;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.] \/ ].s, q.]);

      then x in [.r, p.] or x in ].s, q.] by XBOOLE_0:def 3;

      then

       A7: r <= x & x <= p or s < x & x <= q by Th1, Th2;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.] by A8, Th1;

       not x in ].p, s.] by A7, Th2;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:309

    

     Th309: r <= s & p <= q implies ( ].r, q.[ \ [.p, s.]) = ( ].r, p.[ \/ ].s, q.[)

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be Real;

      thus x in ( ].r, q.[ \ [.p, s.]) implies x in ( ].r, p.[ \/ ].s, q.[)

      proof

        assume

         A3: x in ( ].r, q.[ \ [.p, s.]);

        then

         A4: not x in [.p, s.] by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th4;

        

         A6: x < q by A3, Th4;

         not (p <= x & x <= s) by A4, Th1;

        then x in ].r, p.[ or x in ].s, q.[ by A5, A6, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.[ \/ ].s, q.[);

      then x in ].r, p.[ or x in ].s, q.[ by XBOOLE_0:def 3;

      then

       A7: r < x & x < p or s < x & x < q by Th4;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.[ by A8, Th4;

       not x in [.p, s.] by A7, Th1;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:310

    

     Th310: r <= s & p <= q implies ( [.r, q.[ \ [.p, s.]) = ( [.r, p.[ \/ ].s, q.[)

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.[ \ [.p, s.]) implies x in ( [.r, p.[ \/ ].s, q.[)

      proof

        assume

         A3: x in ( [.r, q.[ \ [.p, s.]);

        then

         A4: not x in [.p, s.] by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th3;

        

         A6: x < q by A3, Th3;

         not (p <= x & x <= s) by A4, Th1;

        then x in [.r, p.[ or x in ].s, q.[ by A5, A6, Th3, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.[ \/ ].s, q.[);

      then x in [.r, p.[ or x in ].s, q.[ by XBOOLE_0:def 3;

      then

       A7: r <= x & x < p or s < x & x < q by Th3, Th4;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x < q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.[ by A8, Th3;

       not x in [.p, s.] by A7, Th1;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:311

    

     Th311: r < s & p <= q implies ( ].r, q.] \ [.p, s.]) = ( ].r, p.[ \/ ].s, q.])

    proof

      assume that

       A1: r < s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( ].r, q.] \ [.p, s.]) implies x in ( ].r, p.[ \/ ].s, q.])

      proof

        assume

         A3: x in ( ].r, q.] \ [.p, s.]);

        then

         A4: not x in [.p, s.] by XBOOLE_0:def 5;

        

         A5: r < x by A3, Th2;

        

         A6: x <= q by A3, Th2;

         not (p <= x & x <= s) by A4, Th1;

        then x in ].r, p.[ or x in ].s, q.] by A5, A6, Th2, Th4;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( ].r, p.[ \/ ].s, q.]);

      then x in ].r, p.[ or x in ].s, q.] by XBOOLE_0:def 3;

      then

       A7: r < x & x < p or s < x & x <= q by Th2, Th4;

      then

       A8: r < x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in ].r, q.] by A8, Th2;

       not x in [.p, s.] by A7, Th1;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:312

    

     Th312: r <= s & p <= q implies ( [.r, q.] \ [.p, s.]) = ( [.r, p.[ \/ ].s, q.])

    proof

      assume that

       A1: r <= s and

       A2: p <= q;

      let x be ExtReal;

      thus x in ( [.r, q.] \ [.p, s.]) implies x in ( [.r, p.[ \/ ].s, q.])

      proof

        assume

         A3: x in ( [.r, q.] \ [.p, s.]);

        then

         A4: not x in [.p, s.] by XBOOLE_0:def 5;

        

         A5: r <= x by A3, Th1;

        

         A6: x <= q by A3, Th1;

         not (p <= x & x <= s) by A4, Th1;

        then x in [.r, p.[ or x in ].s, q.] by A5, A6, Th2, Th3;

        hence thesis by XBOOLE_0:def 3;

      end;

      assume x in ( [.r, p.[ \/ ].s, q.]);

      then x in [.r, p.[ or x in ].s, q.] by XBOOLE_0:def 3;

      then

       A7: r <= x & x < p or s < x & x <= q by Th2, Th3;

      then

       A8: r <= x by A1, XXREAL_0: 2;

      x <= q by A2, A7, XXREAL_0: 2;

      then

       A9: x in [.r, q.] by A8, Th1;

       not x in [.p, s.] by A7, Th1;

      hence thesis by A9, XBOOLE_0:def 5;

    end;

    theorem :: XXREAL_1:313

    

     Th313: r <= p & p <= q implies ( ].r, q.[ \ {p}) = ( ].r, p.[ \/ ].p, q.[)

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th309;

    end;

    theorem :: XXREAL_1:314

    

     Th314: r <= p & p <= q implies ( [.r, q.[ \ {p}) = ( [.r, p.[ \/ ].p, q.[)

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th310;

    end;

    theorem :: XXREAL_1:315

    

     Th315: r < p & p <= q implies ( ].r, q.] \ {p}) = ( ].r, p.[ \/ ].p, q.])

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th311;

    end;

    theorem :: XXREAL_1:316

    

     Th316: r <= p & p <= q implies ( [.r, q.] \ {p}) = ( [.r, p.[ \/ ].p, q.])

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th312;

    end;

    theorem :: XXREAL_1:317

    

     Th317: r < q & p <= q implies ( ].r, q.] \ ].p, q.[) = ( ].r, p.] \/ {q})

    proof

       [.q, q.] = {q} by Th17;

      hence thesis by Th299;

    end;

    theorem :: XXREAL_1:318

    

     Th318: r <= q & p <= q implies ( [.r, q.] \ ].p, q.[) = ( [.r, p.] \/ {q})

    proof

       [.q, q.] = {q} by Th17;

      hence thesis by Th300;

    end;

    theorem :: XXREAL_1:319

    

     Th319: r < q & p <= q implies ( ].r, q.] \ [.p, q.[) = ( ].r, p.[ \/ {q})

    proof

       [.q, q.] = {q} by Th17;

      hence thesis by Th303;

    end;

    theorem :: XXREAL_1:320

    

     Th320: r <= q & p <= q implies ( [.r, q.] \ [.p, q.[) = ( [.r, p.[ \/ {q})

    proof

       [.q, q.] = {q} by Th17;

      hence thesis by Th304;

    end;

    theorem :: XXREAL_1:321

    

     Th321: p <= s & p < q implies ( [.p, q.[ \ ].p, s.[) = ( {p} \/ [.s, q.[)

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th298;

    end;

    theorem :: XXREAL_1:322

    

     Th322: p <= s & p <= q implies ( [.p, q.] \ ].p, s.[) = ( {p} \/ [.s, q.])

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th300;

    end;

    theorem :: XXREAL_1:323

    

     Th323: p <= s & p < q implies ( [.p, q.[ \ ].p, s.]) = ( {p} \/ ].s, q.[)

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th306;

    end;

    theorem :: XXREAL_1:324

    

     Th324: p <= s & p <= q implies ( [.p, q.] \ ].p, s.]) = ( {p} \/ ].s, q.])

    proof

       [.p, p.] = {p} by Th17;

      hence thesis by Th308;

    end;

    theorem :: XXREAL_1:325

    

     Th325: p < q implies ( [. -infty , q.[ \ ].p, s.[) = ( [. -infty , p.] \/ [.s, q.[) by Th298, XXREAL_0: 5;

    theorem :: XXREAL_1:326

    

     Th326: p <= q implies ( [. -infty , q.] \ ].p, s.[) = ( [. -infty , p.] \/ [.s, q.])

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th300;

    end;

    theorem :: XXREAL_1:327

    

     Th327: p <= q implies ( [. -infty , q.[ \ [.p, s.[) = ( [. -infty , p.[ \/ [.s, q.[)

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th302;

    end;

    theorem :: XXREAL_1:328

    

     Th328: p <= q implies ( [. -infty , q.] \ [.p, s.[) = ( [. -infty , p.[ \/ [.s, q.])

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th304;

    end;

    theorem :: XXREAL_1:329

    

     Th329: p < q implies ( [. -infty , q.[ \ ].p, s.]) = ( [. -infty , p.] \/ ].s, q.[) by Th306, XXREAL_0: 5;

    theorem :: XXREAL_1:330

    

     Th330: p <= q implies ( [. -infty , q.] \ ].p, s.]) = ( [. -infty , p.] \/ ].s, q.])

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th308;

    end;

    theorem :: XXREAL_1:331

    

     Th331: p <= q implies ( [. -infty , q.[ \ [.p, s.]) = ( [. -infty , p.[ \/ ].s, q.[)

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th310;

    end;

    theorem :: XXREAL_1:332

    

     Th332: p <= q implies ( [. -infty , q.] \ [.p, s.]) = ( [. -infty , p.[ \/ ].s, q.])

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th312;

    end;

    theorem :: XXREAL_1:333

    

     Th333: for s be Real holds p < q implies ( ]. -infty , q.[ \ ].p, s.[) = ( ]. -infty , p.] \/ [.s, q.[)

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      then -infty < s by XXREAL_0: 12;

      hence thesis by Th297;

    end;

    theorem :: XXREAL_1:334

    

     Th334: for s be Real holds p <= q implies ( ]. -infty , q.] \ ].p, s.[) = ( ]. -infty , p.] \/ [.s, q.])

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th299, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:335

    

     Th335: for s be Real holds p <= q implies ( ]. -infty , q.[ \ [.p, s.[) = ( ]. -infty , p.[ \/ [.s, q.[)

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th301, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:336

    

     Th336: for s be Real holds p <= q implies ( ]. -infty , q.] \ [.p, s.[) = ( ]. -infty , p.[ \/ [.s, q.])

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th303, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:337

    

     Th337: for s be Real holds p < q implies ( ]. -infty , q.[ \ ].p, s.]) = ( ]. -infty , p.] \/ ].s, q.[)

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      then -infty < s by XXREAL_0: 12;

      hence thesis by Th305;

    end;

    theorem :: XXREAL_1:338

    

     Th338: for s be Real holds p <= q implies ( ]. -infty , q.] \ ].p, s.]) = ( ]. -infty , p.] \/ ].s, q.])

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th307, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:339

    

     Th339: p <= q implies ( ]. -infty , q.[ \ [.p, s.]) = ( ]. -infty , p.[ \/ ].s, q.[)

    proof

       -infty <= s by XXREAL_0: 5;

      hence thesis by Th309;

    end;

    theorem :: XXREAL_1:340

    

     Th340: for s be Real holds p <= q implies ( ]. -infty , q.] \ [.p, s.]) = ( ]. -infty , p.[ \/ ].s, q.])

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th311, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:341

    

     Th341: p <= q implies ( [. -infty , q.[ \ {p}) = ( [. -infty , p.[ \/ ].p, q.[)

    proof

       -infty <= p by XXREAL_0: 5;

      hence thesis by Th314;

    end;

    theorem :: XXREAL_1:342

    

     Th342: p <= q implies ( [. -infty , q.] \ {p}) = ( [. -infty , p.[ \/ ].p, q.])

    proof

       -infty <= p by XXREAL_0: 5;

      hence thesis by Th316;

    end;

    theorem :: XXREAL_1:343

    p <= q implies ( [. -infty , q.] \ ].p, q.[) = ( [. -infty , p.] \/ {q})

    proof

       -infty <= q by XXREAL_0: 5;

      hence thesis by Th318;

    end;

    theorem :: XXREAL_1:344

    p <= q implies ( [. -infty , q.] \ [.p, q.[) = ( [. -infty , p.[ \/ {q})

    proof

       -infty <= q by XXREAL_0: 5;

      hence thesis by Th320;

    end;

    theorem :: XXREAL_1:345

    ( [. -infty , q.] \ ]. -infty , s.[) = ( { -infty } \/ [.s, q.])

    proof

      

       A1: -infty <= s by XXREAL_0: 5;

       -infty <= q by XXREAL_0: 5;

      hence thesis by A1, Th322;

    end;

    theorem :: XXREAL_1:346

    ( [. -infty , q.] \ ]. -infty , s.]) = ( { -infty } \/ ].s, q.])

    proof

      

       A1: -infty <= s by XXREAL_0: 5;

       -infty <= q by XXREAL_0: 5;

      hence thesis by A1, Th324;

    end;

    theorem :: XXREAL_1:347

    for q be Real holds ( [. -infty , q.[ \ ]. -infty , s.[) = ( { -infty } \/ [.s, q.[)

    proof

      let q be Real;

      

       A1: q in REAL by XREAL_0:def 1;

       -infty <= s by XXREAL_0: 5;

      hence thesis by A1, Th321, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:348

    for q be Real holds ( [. -infty , q.[ \ ]. -infty , s.]) = ( { -infty } \/ ].s, q.[)

    proof

      let q be Real;

      

       A1: q in REAL by XREAL_0:def 1;

       -infty <= s by XXREAL_0: 5;

      hence thesis by A1, Th323, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:349

    

     Th349: p <= q implies ( ]. -infty , q.[ \ {p}) = ( ]. -infty , p.[ \/ ].p, q.[)

    proof

       -infty <= p by XXREAL_0: 5;

      hence thesis by Th313;

    end;

    theorem :: XXREAL_1:350

    

     Th350: for p be Real holds p <= q implies ( ]. -infty , q.] \ {p}) = ( ]. -infty , p.[ \/ ].p, q.])

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th315, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:351

    for q be Real holds p <= q implies ( ]. -infty , q.] \ ].p, q.[) = ( ]. -infty , p.] \/ {q})

    proof

      let q be Real;

      q in REAL by XREAL_0:def 1;

      hence thesis by Th317, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:352

    for q be Real holds p <= q implies ( ]. -infty , q.] \ [.p, q.[) = ( ]. -infty , p.[ \/ {q})

    proof

      let q be Real;

      q in REAL by XREAL_0:def 1;

      hence thesis by Th319, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:353

    r < s implies ( ].r, +infty .] \ ].p, s.[) = ( ].r, p.] \/ [.s, +infty .]) by Th299, XXREAL_0: 3;

    theorem :: XXREAL_1:354

    r <= s implies ( [.r, +infty .] \ ].p, s.[) = ( [.r, p.] \/ [.s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th300;

    end;

    theorem :: XXREAL_1:355

    r < s implies ( ].r, +infty .[ \ [.p, s.[) = ( ].r, p.[ \/ [.s, +infty .[) by Th301, XXREAL_0: 3;

    theorem :: XXREAL_1:356

    r <= s implies ( [.r, +infty .[ \ [.p, s.[) = ( [.r, p.[ \/ [.s, +infty .[)

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th302;

    end;

    theorem :: XXREAL_1:357

    r < s implies ( ].r, +infty .] \ [.p, s.[) = ( ].r, p.[ \/ [.s, +infty .]) by Th303, XXREAL_0: 3;

    theorem :: XXREAL_1:358

    r <= s implies ( [.r, +infty .] \ [.p, s.[) = ( [.r, p.[ \/ [.s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th304;

    end;

    theorem :: XXREAL_1:359

    r < s implies ( ].r, +infty .] \ ].p, s.]) = ( ].r, p.] \/ ].s, +infty .]) by Th307, XXREAL_0: 3;

    theorem :: XXREAL_1:360

    r <= s implies ( [.r, +infty .] \ ].p, s.]) = ( [.r, p.] \/ ].s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th308;

    end;

    theorem :: XXREAL_1:361

    r <= s implies ( ].r, +infty .[ \ [.p, s.]) = ( ].r, p.[ \/ ].s, +infty .[)

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th309;

    end;

    theorem :: XXREAL_1:362

    r <= s implies ( [.r, +infty .[ \ [.p, s.]) = ( [.r, p.[ \/ ].s, +infty .[)

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th310;

    end;

    theorem :: XXREAL_1:363

    r < s implies ( ].r, +infty .] \ [.p, s.]) = ( ].r, p.[ \/ ].s, +infty .]) by Th311, XXREAL_0: 3;

    theorem :: XXREAL_1:364

    r <= s implies ( [.r, +infty .] \ [.p, s.]) = ( [.r, p.[ \/ ].s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th312;

    end;

    theorem :: XXREAL_1:365

    r <= p implies ( ].r, +infty .[ \ {p}) = ( ].r, p.[ \/ ].p, +infty .[)

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th313;

    end;

    theorem :: XXREAL_1:366

    r <= p implies ( [.r, +infty .[ \ {p}) = ( [.r, p.[ \/ ].p, +infty .[)

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th314;

    end;

    theorem :: XXREAL_1:367

    r < p implies ( ].r, +infty .] \ {p}) = ( ].r, p.[ \/ ].p, +infty .]) by Th315, XXREAL_0: 3;

    theorem :: XXREAL_1:368

    r <= p implies ( [.r, +infty .] \ {p}) = ( [.r, p.[ \/ ].p, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th316;

    end;

    theorem :: XXREAL_1:369

    ( [.r, +infty .] \ ].p, +infty .[) = ( [.r, p.] \/ { +infty })

    proof

      

       A1: r <= +infty by XXREAL_0: 3;

      p <= +infty by XXREAL_0: 3;

      hence thesis by A1, Th318;

    end;

    theorem :: XXREAL_1:370

    ( [.r, +infty .] \ [.p, +infty .[) = ( [.r, p.[ \/ { +infty })

    proof

      

       A1: r <= +infty by XXREAL_0: 3;

      p <= +infty by XXREAL_0: 3;

      hence thesis by A1, Th320;

    end;

    theorem :: XXREAL_1:371

    for r be Real holds ( ].r, +infty .] \ ].p, +infty .[) = ( ].r, p.] \/ { +infty })

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      then r < +infty by XXREAL_0: 9;

      hence thesis by Th317, XXREAL_0: 3;

    end;

    theorem :: XXREAL_1:372

    for r be Real holds ( ].r, +infty .] \ [.p, +infty .[) = ( ].r, p.[ \/ { +infty })

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      then r < +infty by XXREAL_0: 9;

      hence thesis by Th319, XXREAL_0: 3;

    end;

    theorem :: XXREAL_1:373

    p <= s implies ( [.p, +infty .] \ ].p, s.[) = ( {p} \/ [.s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th322;

    end;

    theorem :: XXREAL_1:374

    p <= s implies ( [.p, +infty .] \ ].p, s.]) = ( {p} \/ ].s, +infty .])

    proof

      p <= +infty by XXREAL_0: 3;

      hence thesis by Th324;

    end;

    theorem :: XXREAL_1:375

    ( [. -infty , +infty .] \ ].p, s.[) = ( [. -infty , p.] \/ [.s, +infty .]) by Th326, XXREAL_0: 3;

    theorem :: XXREAL_1:376

    ( [. -infty , +infty .[ \ [.p, s.[) = ( [. -infty , p.[ \/ [.s, +infty .[) by Th327, XXREAL_0: 3;

    theorem :: XXREAL_1:377

    ( [. -infty , +infty .] \ [.p, s.[) = ( [. -infty , p.[ \/ [.s, +infty .]) by Th328, XXREAL_0: 3;

    theorem :: XXREAL_1:378

    ( [. -infty , +infty .] \ ].p, s.]) = ( [. -infty , p.] \/ ].s, +infty .]) by Th330, XXREAL_0: 3;

    theorem :: XXREAL_1:379

    ( [. -infty , +infty .[ \ [.p, s.]) = ( [. -infty , p.[ \/ ].s, +infty .[) by Th331, XXREAL_0: 3;

    theorem :: XXREAL_1:380

    ( [. -infty , +infty .] \ [.p, s.]) = ( [. -infty , p.[ \/ ].s, +infty .]) by Th332, XXREAL_0: 3;

    theorem :: XXREAL_1:381

    for s be Real holds ( ]. -infty , +infty .] \ ].p, s.[) = ( ]. -infty , p.] \/ [.s, +infty .]) by Th334, XXREAL_0: 3;

    theorem :: XXREAL_1:382

    for s be Real holds ( REAL \ [.p, s.[) = ( ]. -infty , p.[ \/ [.s, +infty .[) by Th224, Th335, XXREAL_0: 3;

    theorem :: XXREAL_1:383

    for s be Real holds ( ]. -infty , +infty .] \ [.p, s.[) = ( ]. -infty , p.[ \/ [.s, +infty .]) by Th336, XXREAL_0: 3;

    theorem :: XXREAL_1:384

    for s be Real holds ( ]. -infty , +infty .] \ ].p, s.]) = ( ]. -infty , p.] \/ ].s, +infty .]) by Th338, XXREAL_0: 3;

    theorem :: XXREAL_1:385

    ( REAL \ [.p, s.]) = ( ]. -infty , p.[ \/ ].s, +infty .[) by Th224, Th339, XXREAL_0: 3;

    theorem :: XXREAL_1:386

    for s be Real holds ( ]. -infty , +infty .] \ [.p, s.]) = ( ]. -infty , p.[ \/ ].s, +infty .]) by Th340, XXREAL_0: 3;

    theorem :: XXREAL_1:387

    ( [. -infty , +infty .[ \ {p}) = ( [. -infty , p.[ \/ ].p, +infty .[) by Th341, XXREAL_0: 3;

    theorem :: XXREAL_1:388

    ( [. -infty , +infty .] \ {p}) = ( [. -infty , p.[ \/ ].p, +infty .]) by Th342, XXREAL_0: 3;

    theorem :: XXREAL_1:389

    ( REAL \ {p}) = ( ]. -infty , p.[ \/ ].p, +infty .[) by Th224, Th349, XXREAL_0: 3;

    theorem :: XXREAL_1:390

    for p be Real holds ( ]. -infty , +infty .] \ {p}) = ( ]. -infty , p.[ \/ ].p, +infty .]) by Th350, XXREAL_0: 3;

    theorem :: XXREAL_1:391

    for p be Real holds r < s implies ( ].r, +infty .[ \ ].p, s.[) = ( ].r, p.] \/ [.s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      then p < +infty by XXREAL_0: 9;

      hence thesis by Th297;

    end;

    theorem :: XXREAL_1:392

    for p be Real holds r <= s implies ( [.r, +infty .[ \ ].p, s.[) = ( [.r, p.] \/ [.s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th298, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:393

    for p be Real holds r < s implies ( ].r, +infty .[ \ ].p, s.]) = ( ].r, p.] \/ ].s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      then p < +infty by XXREAL_0: 9;

      hence thesis by Th305;

    end;

    theorem :: XXREAL_1:394

    for p be Real holds r <= s implies ( [.r, +infty .[ \ ].p, s.]) = ( [.r, p.] \/ ].s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th306, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:395

    for p be Real holds p <= s implies ( [.p, +infty .[ \ ].p, s.]) = ( {p} \/ ].s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th323, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:396

    for p be Real holds ( [. -infty , +infty .[ \ ].p, s.[) = ( [. -infty , p.] \/ [.s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th325, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:397

    for p be Real holds ( [. -infty , +infty .[ \ ].p, s.]) = ( [. -infty , p.] \/ ].s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th329, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:398

    for s,p be Real holds ( REAL \ ].p, s.[) = ( ]. -infty , p.] \/ [.s, +infty .[)

    proof

      let s,p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th224, Th333, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:399

    for s,p be Real holds ( REAL \ ].p, s.]) = ( ]. -infty , p.] \/ ].s, +infty .[)

    proof

      let s,p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th224, Th337, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:400

    for p be Real holds p <= s implies ( [.p, +infty .[ \ ].p, s.[) = ( {p} \/ [.s, +infty .[)

    proof

      let p be Real;

      p in REAL by XREAL_0:def 1;

      hence thesis by Th321, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:401

    

     Th401: r < s implies ( [.r, s.] \ [.r, s.[) = {s}

    proof

       [.s, s.] = {s} by Th17;

      hence thesis by Th184;

    end;

    theorem :: XXREAL_1:402

    

     Th402: r < s implies ( ].r, s.] \ ].r, s.[) = {s}

    proof

       [.s, s.] = {s} by Th17;

      hence thesis by Th188;

    end;

    theorem :: XXREAL_1:403

    

     Th403: r < t implies ( [.r, t.] \ ].r, t.]) = {r}

    proof

       [.r, r.] = {r} by Th17;

      hence thesis by Th192;

    end;

    theorem :: XXREAL_1:404

    

     Th404: r < t implies ( [.r, t.[ \ ].r, t.[) = {r}

    proof

       [.r, r.] = {r} by Th17;

      hence thesis by Th196;

    end;

    theorem :: XXREAL_1:405

    for s be Real holds ( [. -infty , s.] \ [. -infty , s.[) = {s}

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th401, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:406

    for s be Real holds ( ]. -infty , s.] \ ]. -infty , s.[) = {s}

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th402, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:407

    for s be Real holds ( [. -infty , s.] \ ]. -infty , s.]) = { -infty }

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th403, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:408

    for s be Real holds ( [. -infty , s.[ \ ]. -infty , s.[) = { -infty }

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th404, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:409

    for s be Real holds ( [.s, +infty .] \ [.s, +infty .[) = { +infty }

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th401, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:410

    for s be Real holds ( ].s, +infty .] \ ].s, +infty .[) = { +infty }

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th402, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:411

    for s be Real holds ( [.s, +infty .] \ ].s, +infty .]) = {s}

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th403, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:412

    for s be Real holds ( [.s, +infty .[ \ ].s, +infty .[) = {s}

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th404, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:413

    r <= s & s < t implies ( [.r, s.] \/ [.s, t.[) = [.r, t.[

    proof

      assume that

       A1: r <= s and

       A2: s < t;

      let p;

      thus p in ( [.r, s.] \/ [.s, t.[) implies p in [.r, t.[

      proof

        assume p in ( [.r, s.] \/ [.s, t.[);

        then p in [.r, s.] or p in [.s, t.[ by XBOOLE_0:def 3;

        then

         A3: r <= p & p <= s or s <= p & p < t by Th1, Th3;

        then

         A4: r <= p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th3;

      end;

      assume p in [.r, t.[;

      then r <= p & p <= s or s <= p & p < t by Th3;

      then p in [.r, s.] or p in [.s, t.[ by Th1, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:414

    r < s & s <= t implies ( ].r, s.] \/ [.s, t.]) = ].r, t.]

    proof

      assume that

       A1: r < s and

       A2: s <= t;

      let p;

      thus p in ( ].r, s.] \/ [.s, t.]) implies p in ].r, t.]

      proof

        assume p in ( ].r, s.] \/ [.s, t.]);

        then p in ].r, s.] or p in [.s, t.] by XBOOLE_0:def 3;

        then

         A3: r < p & p <= s or s <= p & p <= t by Th1, Th2;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p <= t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th2;

      end;

      assume p in ].r, t.];

      then r < p & p <= s or s <= p & p <= t by Th2;

      then p in ].r, s.] or p in [.s, t.] by Th1, Th2;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:415

    r < s & s < t implies ( ].r, s.] \/ [.s, t.[) = ].r, t.[

    proof

      assume that

       A1: r < s and

       A2: s < t;

      let p;

      thus p in ( ].r, s.] \/ [.s, t.[) implies p in ].r, t.[

      proof

        assume p in ( ].r, s.] \/ [.s, t.[);

        then p in ].r, s.] or p in [.s, t.[ by XBOOLE_0:def 3;

        then

         A3: r < p & p <= s or s <= p & p < t by Th2, Th3;

        then

         A4: r < p by A1, XXREAL_0: 2;

        p < t by A2, A3, XXREAL_0: 2;

        hence thesis by A4, Th4;

      end;

      assume p in ].r, t.[;

      then r < p & p <= s or s <= p & p < t by Th4;

      then p in ].r, s.] or p in [.s, t.[ by Th2, Th3;

      hence thesis by XBOOLE_0:def 3;

    end;

    theorem :: XXREAL_1:416

    r <= s & s < t implies ( [.r, s.] /\ [.s, t.[) = {s}

    proof

      assume that

       A1: r <= s and

       A2: s < t;

      now

        let x be object;

        hereby

          assume

           A3: x in ( [.r, s.] /\ [.s, t.[);

          then

          reconsider p = x as ExtReal;

          

           A4: p in [.r, s.] by A3, XBOOLE_0:def 4;

          p in [.s, t.[ by A3, XBOOLE_0:def 4;

          then

           A5: s <= p by Th3;

          p <= s by A4, Th1;

          hence x = s by A5, XXREAL_0: 1;

        end;

        assume

         A6: x = s;

        

         A7: s in [.r, s.] by A1, Th1;

        s in [.s, t.[ by A2, Th3;

        hence x in ( [.r, s.] /\ [.s, t.[) by A6, A7, XBOOLE_0:def 4;

      end;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:417

    r < s & s <= t implies ( ].r, s.] /\ [.s, t.]) = {s}

    proof

      assume that

       A1: r < s and

       A2: s <= t;

      now

        let x be object;

        hereby

          assume

           A3: x in ( ].r, s.] /\ [.s, t.]);

          then

          reconsider p = x as ExtReal;

          

           A4: p in ].r, s.] by A3, XBOOLE_0:def 4;

          p in [.s, t.] by A3, XBOOLE_0:def 4;

          then

           A5: s <= p by Th1;

          p <= s by A4, Th2;

          hence x = s by A5, XXREAL_0: 1;

        end;

        assume

         A6: x = s;

        

         A7: s in ].r, s.] by A1, Th2;

        s in [.s, t.] by A2, Th1;

        hence x in ( ].r, s.] /\ [.s, t.]) by A6, A7, XBOOLE_0:def 4;

      end;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:418

    r <= s & s <= t implies ( [.r, s.] /\ [.s, t.]) = {s}

    proof

      assume that

       A1: r <= s and

       A2: s <= t;

      now

        let x be object;

        hereby

          assume

           A3: x in ( [.r, s.] /\ [.s, t.]);

          then

          reconsider p = x as ExtReal;

          

           A4: p in [.r, s.] by A3, XBOOLE_0:def 4;

          p in [.s, t.] by A3, XBOOLE_0:def 4;

          then

           A5: s <= p by Th1;

          p <= s by A4, Th1;

          hence x = s by A5, XXREAL_0: 1;

        end;

        assume

         A6: x = s;

        

         A7: s in [.r, s.] by A1, Th1;

        s in [.s, t.] by A2, Th1;

        hence x in ( [.r, s.] /\ [.s, t.]) by A6, A7, XBOOLE_0:def 4;

      end;

      hence thesis by TARSKI:def 1;

    end;

    theorem :: XXREAL_1:419

     [. -infty , s.] = ( ]. -infty , s.[ \/ { -infty , s}) by Th128, XXREAL_0: 5;

    theorem :: XXREAL_1:420

     [. -infty , s.] = ( [. -infty , s.[ \/ {s}) by Th129, XXREAL_0: 5;

    theorem :: XXREAL_1:421

     [. -infty , s.] = ( { -infty } \/ ]. -infty , s.]) by Th130, XXREAL_0: 5;

    theorem :: XXREAL_1:422

    for s be Real holds [. -infty , s.[ = ( { -infty } \/ ]. -infty , s.[)

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th131, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:423

    for s be Real holds ]. -infty , s.] = ( ]. -infty , s.[ \/ {s})

    proof

      let s be Real;

      s in REAL by XREAL_0:def 1;

      hence thesis by Th132, XXREAL_0: 12;

    end;

    theorem :: XXREAL_1:424

     [.r, +infty .] = ( ].r, +infty .[ \/ {r, +infty }) by Th128, XXREAL_0: 3;

    theorem :: XXREAL_1:425

     [.r, +infty .] = ( [.r, +infty .[ \/ { +infty }) by Th129, XXREAL_0: 3;

    theorem :: XXREAL_1:426

     [.r, +infty .] = ( {r} \/ ].r, +infty .]) by Th130, XXREAL_0: 3;

    theorem :: XXREAL_1:427

    for r be Real holds [.r, +infty .[ = ( {r} \/ ].r, +infty .[)

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      hence thesis by Th131, XXREAL_0: 9;

    end;

    theorem :: XXREAL_1:428

    for r be Real holds ].r, +infty .] = ( ].r, +infty .[ \/ { +infty })

    proof

      let r be Real;

      r in REAL by XREAL_0:def 1;

      hence thesis by Th132, XXREAL_0: 9;

    end;