parsp_1.miz



    begin

    reserve F for Field,

a,b,c,d,e,f,g,h for Element of F;

    

     Lm1: for F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b be Element of F holds ( - (a - b)) = (b - a)

    proof

      let F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b be Element of F;

      

      thus ( - (a - b)) = (b + ( - a)) by RLVECT_1: 33

      .= (b - a) by RLVECT_1:def 11;

    end;

    

     Lm2: (((a - b) * (c - d)) - ((b - a) * (d - c))) = ( 0. F)

    proof

      ( - (a - b)) = (b - a) & ( - (c - d)) = (d - c) by Lm1;

      then (((a - b) * (c - d)) - ((b - a) * (d - c))) = (((a - b) * (c - d)) - ((a - b) * (c - d))) by VECTSP_1: 10;

      hence thesis by RLVECT_1: 15;

    end;

    

     Lm3: ((a * (b - b)) - ((c - c) * d)) = ( 0. F)

    proof

      (c - c) = ( 0. F) by RLVECT_1: 15;

      then

       A1: ((c - c) * d) = ( 0. F);

      (b - b) = ( 0. F) by RLVECT_1: 15;

      then (a * (b - b)) = ( 0. F);

      hence thesis by A1, RLVECT_1: 15;

    end;

    

     Lm4: a <> ( 0. F) & ((a * e) - (d * b)) = ( 0. F) & ((a * c) - (h * b)) = ( 0. F) implies ((d * c) - (h * e)) = ( 0. F)

    proof

      assume that

       A1: a <> ( 0. F) and

       A2: ((a * e) - (d * b)) = ( 0. F) and

       A3: ((a * c) - (h * b)) = ( 0. F);

      c = ((h * b) * (a " )) by A1, A3, VECTSP_1: 30;

      then c = (h * (b * (a " ))) by GROUP_1:def 3;

      then

       A4: (d * c) = ((d * h) * (b * (a " ))) by GROUP_1:def 3;

      e = ((d * b) * (a " )) by A1, A2, VECTSP_1: 30;

      then e = (d * (b * (a " ))) by GROUP_1:def 3;

      then (h * e) = ((h * d) * (b * (a " ))) by GROUP_1:def 3;

      hence thesis by A4, RLVECT_1: 15;

    end;

    

     Lm5: ((a * b) - (c * d)) = ( 0. F) implies ((d * c) - (b * a)) = ( 0. F)

    proof

      assume ((a * b) - (c * d)) = ( 0. F);

      then

       A1: ( - ((a * b) - (c * d))) = ( 0. F) by RLVECT_1: 12;

      

      thus ((d * c) - (b * a)) = ((d * c) + ( - (b * a))) by RLVECT_1:def 11

      .= ( 0. F) by A1, RLVECT_1: 33;

    end;

    

     Lm6: b <> ( 0. F) & ((a * e) - (d * b)) = ( 0. F) & ((a * c) - (h * b)) = ( 0. F) implies ((d * c) - (h * e)) = ( 0. F)

    proof

      assume b <> ( 0. F);

      then ((b * d) - (e * a)) = ( 0. F) & ((b * h) - (c * a)) = ( 0. F) implies ((e * h) - (c * d)) = ( 0. F) by Lm4;

      hence thesis by Lm5;

    end;

    

     Lm7: ((c * d) * (a * b)) = (((a * c) * d) * b)

    proof

      

      thus ((c * d) * (a * b)) = ((a * (c * d)) * b) by GROUP_1:def 3

      .= (((a * c) * d) * b) by GROUP_1:def 3;

    end;

    

     Lm8: ((a * b) - (c * d)) = ( 0. F) implies ((((a * f) * g) * b) - (((c * f) * g) * d)) = ( 0. F)

    proof

      assume

       A1: ((a * b) - (c * d)) = ( 0. F);

      (((a * f) * g) * b) = ((f * g) * (a * b)) & (((c * f) * g) * d) = ((f * g) * (c * d)) by Lm7;

      

      hence ((((a * f) * g) * b) - (((c * f) * g) * d)) = ((f * g) * ((a * b) - (c * d))) by VECTSP_1: 11

      .= ( 0. F) by A1;

    end;

    

     Lm9: ((a - b) * (c - d)) = ((a * c) + (( - (a * d)) + ( - (b * (c - d)))))

    proof

      

      thus ((a - b) * (c - d)) = ((a + ( - b)) * (c - d)) by RLVECT_1:def 11

      .= ((a * (c - d)) + (( - b) * (c - d))) by VECTSP_1:def 7

      .= ((a * (c - d)) + ( - (b * (c - d)))) by VECTSP_1: 9

      .= (((a * c) - (a * d)) + ( - (b * (c - d)))) by VECTSP_1: 11

      .= (((a * c) + ( - (a * d))) + ( - (b * (c - d)))) by RLVECT_1:def 11

      .= ((a * c) + (( - (a * d)) + ( - (b * (c - d))))) by RLVECT_1:def 3;

    end;

    

     Lm10: ((a + b) + (c + d)) = ((a + (b + c)) + d)

    proof

      

      thus ((a + b) + (c + d)) = (((a + b) + c) + d) by RLVECT_1:def 3

      .= ((a + (b + c)) + d) by RLVECT_1:def 3;

    end;

    

     Lm11: for F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b,c be Element of F holds ((b + a) - (c + a)) = (b - c)

    proof

      let F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b,c be Element of F;

      

      thus ((b + a) - (c + a)) = ((b + a) + ( - (c + a))) by RLVECT_1:def 11

      .= ((b + a) + (( - a) + ( - c))) by RLVECT_1: 31

      .= (((b + a) + ( - a)) + ( - c)) by RLVECT_1:def 3

      .= ((b + (a + ( - a))) + ( - c)) by RLVECT_1:def 3

      .= ((b + ( 0. F)) + ( - c)) by RLVECT_1:def 10

      .= (b + ( - c)) by RLVECT_1: 4

      .= (b - c) by RLVECT_1:def 11;

    end;

    

     Lm12: for F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b be Element of F holds (a + b) = ( - (( - b) + ( - a)))

    proof

      let F be add-associative right_zeroed right_complementable non empty addLoopStr, a,b be Element of F;

      

      thus (a + b) = ( - ( - (a + b))) by RLVECT_1: 17

      .= ( - (( - b) + ( - a))) by RLVECT_1: 31;

    end;

    

     Lm13: (((a - b) * (c - d)) - ((a - e) * (c - f))) = ( 0. F) implies (((b - a) * (f - d)) - ((b - e) * (f - c))) = ( 0. F)

    proof

      assume

       A1: (((a - b) * (c - d)) - ((a - e) * (c - f))) = ( 0. F);

      

       A2: ((a - b) * (c - d)) = ((a * c) + (( - (a * d)) + ( - (b * (c - d))))) & ((a - e) * (c - f)) = ((a * c) + (( - (a * f)) + ( - (e * (c - f))))) by Lm9;

      ((b - a) * (f - d)) = ((b * f) + (( - (b * d)) + ( - (a * (f - d))))) & ((b - e) * (f - c)) = ((b * f) + (( - (b * c)) + ( - (e * (f - c))))) by Lm9;

      

      hence (((b - a) * (f - d)) - ((b - e) * (f - c))) = ((( - (b * d)) + ( - (a * (f - d)))) - (( - (b * c)) + ( - (e * (f - c))))) by Lm11

      .= ((( - (b * d)) + ( - ((a * f) - (a * d)))) - (( - (b * c)) + ( - (e * (f - c))))) by VECTSP_1: 11

      .= ((( - (b * d)) + (( - (a * f)) + (a * d))) - (( - (b * c)) + ( - (e * (f - c))))) by RLVECT_1: 33

      .= (((( - (b * d)) + (a * d)) + ( - (a * f))) - (( - (b * c)) + ( - (e * (f - c))))) by RLVECT_1:def 3

      .= ((((a * d) + ( - (b * d))) + ( - (a * f))) + ( - (( - (b * c)) + ( - (e * (f - c)))))) by RLVECT_1:def 11

      .= ((((a * d) + ( - (b * d))) + ( - (a * f))) + (( - ( - (b * c))) + ( - ( - (e * (f - c)))))) by RLVECT_1: 31

      .= ((((a * d) + ( - (b * d))) + ( - (a * f))) + ((b * c) + ( - ( - (e * (f - c)))))) by RLVECT_1: 17

      .= ((((a * d) + ( - (b * d))) + ( - (a * f))) + ((b * c) + (e * (f - c)))) by RLVECT_1: 17

      .= ((((a * d) + ( - (b * d))) + (( - (a * f)) + (b * c))) + (e * (f - c))) by Lm10

      .= ((((a * d) + ( - (b * d))) + (b * c)) + (( - (a * f)) + (e * (f - c)))) by Lm10

      .= (((a * d) + (( - (b * d)) + (b * c))) + (( - (a * f)) + (e * (f - c)))) by RLVECT_1:def 3

      .= (((a * d) + ((b * c) - (b * d))) + (( - (a * f)) + (e * (f - c)))) by RLVECT_1:def 11

      .= (((a * d) + (b * (c - d))) + (( - (a * f)) + (e * (f - c)))) by VECTSP_1: 11

      .= (( - (( - (a * d)) + ( - (b * (c - d))))) + (( - (a * f)) + (e * (f - c)))) by Lm12

      .= (( - (( - (a * d)) + ( - (b * (c - d))))) + ( - (( - ( - (a * f))) + ( - (e * (f - c)))))) by Lm12

      .= (( - (( - (a * d)) + ( - (b * (c - d))))) + ( - ((a * f) + ( - (e * (f - c)))))) by RLVECT_1: 17

      .= ( - ((( - (a * d)) + ( - (b * (c - d)))) + ((a * f) + ( - (e * (f - c)))))) by RLVECT_1: 31

      .= ( - ((( - (a * d)) + ( - (b * (c - d)))) + ( - (( - (a * f)) + ( - ( - (e * (f - c)))))))) by Lm12

      .= ( - ((( - (a * d)) + ( - (b * (c - d)))) - (( - (a * f)) + ( - ( - (e * (f - c))))))) by RLVECT_1:def 11

      .= ( - ((( - (a * d)) + ( - (b * (c - d)))) - (( - (a * f)) + ( - (( - (f - c)) * e))))) by VECTSP_1: 9

      .= ( - ((( - (a * d)) + ( - (b * (c - d)))) - (( - (a * f)) + ( - (e * (c - f)))))) by Lm1

      .= ( - ( 0. F)) by A1, A2, Lm11

      .= ( 0. F) by RLVECT_1: 12;

    end;

    

     Lm14: (a - ((a + b) + ( - c))) = (c - b)

    proof

      

      thus (a - ((a + b) + ( - c))) = (a - (a + (b + ( - c)))) by RLVECT_1:def 3

      .= (a - (a + (b - c))) by RLVECT_1:def 11

      .= (a + ( - (a + (b - c)))) by RLVECT_1:def 11

      .= (a + (( - a) + ( - (b - c)))) by RLVECT_1: 31

      .= ((a + ( - a)) + ( - (b - c))) by RLVECT_1:def 3

      .= (( 0. F) + ( - (b - c))) by RLVECT_1:def 10

      .= ( - (b - c)) by RLVECT_1: 4

      .= (c - b) by Lm1;

    end;

    

     Lm15: (((a - b) * (c - ((c + h) + ( - g)))) - ((e - ((e + b) + ( - a))) * (g - h))) = ( 0. F)

    proof

      (c - ((c + h) + ( - g))) = (g - h) & (e - ((e + b) + ( - a))) = (a - b) by Lm14;

      hence thesis by RLVECT_1: 15;

    end;

    reserve x,y for Element of [:the carrier of F, the carrier of F, the carrier of F:];

    deffunc 3F( Field) = [:the carrier of $1, the carrier of $1, the carrier of $1:];

    definition

      let F;

      :: PARSP_1:def1

      func c3add (F) -> BinOp of [:the carrier of F, the carrier of F, the carrier of F:] means

      : Def1: (it . (x,y)) = [((x `1_3 ) + (y `1_3 )), ((x `2_3 ) + (y `2_3 )), ((x `3_3 ) + (y `3_3 ))];

      existence

      proof

        deffunc O( Element of 3F(F), Element of 3F(F)) = [(($1 `1_3 ) + ($2 `1_3 )), (($1 `2_3 ) + ($2 `2_3 )), (($1 `3_3 ) + ($2 `3_3 ))];

        consider f be BinOp of 3F(F) such that

         A1: (f . (x,y)) = O(x,y) from BINOP_1:sch 4;

        take f;

        thus thesis by A1;

      end;

      uniqueness

      proof

        let f,g be BinOp of 3F(F) such that

         A2: (f . (x,y)) = [((x `1_3 ) + (y `1_3 )), ((x `2_3 ) + (y `2_3 )), ((x `3_3 ) + (y `3_3 ))] and

         A3: (g . (x,y)) = [((x `1_3 ) + (y `1_3 )), ((x `2_3 ) + (y `2_3 )), ((x `3_3 ) + (y `3_3 ))];

        (f . (x,y)) = (g . (x,y))

        proof

          

          thus (f . (x,y)) = [((x `1_3 ) + (y `1_3 )), ((x `2_3 ) + (y `2_3 )), ((x `3_3 ) + (y `3_3 ))] by A2

          .= (g . (x,y)) by A3;

        end;

        hence f = g by BINOP_1: 2;

      end;

    end

    definition

      let F, x, y;

      :: PARSP_1:def2

      func x + y -> Element of [:the carrier of F, the carrier of F, the carrier of F:] equals (( c3add F) . (x,y));

      coherence ;

    end

    theorem :: PARSP_1:1

    (x + y) = [((x `1_3 ) + (y `1_3 )), ((x `2_3 ) + (y `2_3 )), ((x `3_3 ) + (y `3_3 ))] by Def1;

    theorem :: PARSP_1:2

    

     Th2: ( [a, b, c] + [f, g, h]) = [(a + f), (b + g), (c + h)]

    proof

      set abc = [a, b, c], fgh = [f, g, h];

      

       A1: (abc `3_3 ) = c & (fgh `1_3 ) = f;

      

       A2: (fgh `2_3 ) = g & (fgh `3_3 ) = h;

      (abc `1_3 ) = a & (abc `2_3 ) = b;

      hence thesis by A1, A2, Def1;

    end;

    definition

      let F;

      :: PARSP_1:def3

      func c3compl (F) -> UnOp of [:the carrier of F, the carrier of F, the carrier of F:] means

      : Def3: (it . x) = [( - (x `1_3 )), ( - (x `2_3 )), ( - (x `3_3 ))];

      existence

      proof

        deffunc O( Element of 3F(F)) = [( - ($1 `1_3 )), ( - ($1 `2_3 )), ( - ($1 `3_3 ))];

        consider f be UnOp of 3F(F) such that

         A1: (f . x) = O(x) from FUNCT_2:sch 4;

        take f;

        thus thesis by A1;

      end;

      uniqueness

      proof

        let f,g be UnOp of 3F(F) such that

         A2: (f . x) = [( - (x `1_3 )), ( - (x `2_3 )), ( - (x `3_3 ))] and

         A3: (g . x) = [( - (x `1_3 )), ( - (x `2_3 )), ( - (x `3_3 ))];

        (f . x) = (g . x)

        proof

          

          thus (f . x) = [( - (x `1_3 )), ( - (x `2_3 )), ( - (x `3_3 ))] by A2

          .= (g . x) by A3;

        end;

        hence f = g by FUNCT_2: 63;

      end;

    end

    definition

      let F, x;

      :: PARSP_1:def4

      func - x -> Element of [:the carrier of F, the carrier of F, the carrier of F:] equals (( c3compl F) . x);

      coherence ;

    end

    theorem :: PARSP_1:3

    ( - x) = [( - (x `1_3 )), ( - (x `2_3 )), ( - (x `3_3 ))] by Def3;

    definition

      ::$Canceled

      struct ( 1-sorted) ParStr (# the carrier -> set,

the CONGR -> Relation of [: the carrier, the carrier:] #)

       attr strict strict;

    end

    registration

      cluster non empty for ParStr;

      existence

      proof

        set A = the non empty set, R = the Relation of [:A, A:];

        take ParStr (# A, R #);

        thus the carrier of ParStr (# A, R #) is non empty;

      end;

    end

    reserve F for Field;

    reserve PS for non empty ParStr;

    definition

      let PS;

      let a,b,c,d be Element of PS;

      :: PARSP_1:def6

      pred a,b '||' c,d means [ [a, b], [c, d]] in the CONGR of PS;

    end

    definition

      let F;

      :: PARSP_1:def7

      func C_3 (F) -> set equals [:the carrier of F, the carrier of F, the carrier of F:];

      coherence ;

    end

    registration

      let F;

      cluster ( C_3 F) -> non empty;

      coherence ;

    end

    definition

      let F;

      :: PARSP_1:def8

      func 4C_3 (F) -> set equals [: [:( C_3 F), ( C_3 F):], [:( C_3 F), ( C_3 F):]:];

      coherence ;

    end

    registration

      let F;

      cluster ( 4C_3 F) -> non empty;

      coherence ;

    end

    reserve x for set,

a,b,c,d,e,f,g,h,i,j,k,l for Element of [:the carrier of F, the carrier of F, the carrier of F:];

    definition

      let F;

      :: PARSP_1:def9

      func PRs (F) -> set means

      : Def8: for x be object holds x in it iff x in ( 4C_3 F) & ex a, b, c, d st x = [ [a, b], [c, d]] & ((((a `1_3 ) - (b `1_3 )) * ((c `2_3 ) - (d `2_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `2_3 ) - (b `2_3 )))) = ( 0. F) & ((((a `1_3 ) - (b `1_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F) & ((((a `2_3 ) - (b `2_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `2_3 ) - (d `2_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F);

      existence

      proof

        defpred P[ object] means ex a, b, c, d st $1 = [ [a, b], [c, d]] & ((((a `1_3 ) - (b `1_3 )) * ((c `2_3 ) - (d `2_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `2_3 ) - (b `2_3 )))) = ( 0. F) & ((((a `1_3 ) - (b `1_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F) & ((((a `2_3 ) - (b `2_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `2_3 ) - (d `2_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F);

        thus ex X be set st for x be object holds x in X iff x in ( 4C_3 F) & P[x] from XBOOLE_0:sch 1;

      end;

      uniqueness

      proof

        defpred CB[ object] means $1 in ( 4C_3 F) & ex a, b, c, d st $1 = [ [a, b], [c, d]] & ((((a `1_3 ) - (b `1_3 )) * ((c `2_3 ) - (d `2_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `2_3 ) - (b `2_3 )))) = ( 0. F) & ((((a `1_3 ) - (b `1_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `1_3 ) - (d `1_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F) & ((((a `2_3 ) - (b `2_3 )) * ((c `3_3 ) - (d `3_3 ))) - (((c `2_3 ) - (d `2_3 )) * ((a `3_3 ) - (b `3_3 )))) = ( 0. F);

        let H1,H2 be set such that

         A1: for x be object holds x in H1 iff CB[x] and

         A2: for x be object holds x in H2 iff CB[x];

        for x be object holds x in H1 iff x in H2

        proof

          let x be object;

          x in H1 iff CB[x] by A1;

          hence thesis by A2;

        end;

        hence thesis by TARSKI: 2;

      end;

    end

    theorem :: PARSP_1:4

    

     Th4: ( PRs F) c= [: [:( C_3 F), ( C_3 F):], [:( C_3 F), ( C_3 F):]:]

    proof

      let x be object;

      ( 4C_3 F) = [: [:( C_3 F), ( C_3 F):], [:( C_3 F), ( C_3 F):]:];

      hence thesis by Def8;

    end;

    definition

      let F;

      :: PARSP_1:def10

      func PR (F) -> Relation of [:( C_3 F), ( C_3 F):] equals ( PRs F);

      coherence by Th4;

    end

    definition

      let F;

      :: PARSP_1:def11

      func MPS (F) -> ParStr equals ParStr (# ( C_3 F), ( PR F) #);

      correctness ;

    end

    registration

      let F;

      cluster ( MPS F) -> strict non empty;

      coherence ;

    end

    theorem :: PARSP_1:5

    the carrier of ( MPS F) = ( C_3 F);

    theorem :: PARSP_1:6

    the CONGR of ( MPS F) = ( PR F);

    reserve a,b,c,d,p,q,r,s for Element of ( MPS F);

    theorem :: PARSP_1:7

    (a,b) '||' (c,d) iff [ [a, b], [c, d]] in ( PR F);

    theorem :: PARSP_1:8

     [ [a, b], [c, d]] in ( PR F) iff ( [ [a, b], [c, d]] in ( 4C_3 F) & ex e, f, g, h st [ [a, b], [c, d]] = [ [e, f], [g, h]] & ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (h `2_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) & ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F)) by Def8;

    theorem :: PARSP_1:9

    

     Th9: (a,b) '||' (c,d) iff ( [ [a, b], [c, d]] in ( 4C_3 F) & ex e, f, g, h st [ [a, b], [c, d]] = [ [e, f], [g, h]] & ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (h `2_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) & ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F)) by Def8;

    theorem :: PARSP_1:10

    the carrier of ( MPS F) = [:the carrier of F, the carrier of F, the carrier of F:];

    theorem :: PARSP_1:11

     [ [a, b], [c, d]] in ( 4C_3 F);

    theorem :: PARSP_1:12

    

     Th12: (a,b) '||' (c,d) iff ex e, f, g, h st [ [a, b], [c, d]] = [ [e, f], [g, h]] & ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (h `2_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) & ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F)

    proof

       [ [a, b], [c, d]] in ( 4C_3 F);

      hence thesis by Th9;

    end;

    theorem :: PARSP_1:13

    

     Th13: (a,b) '||' (b,a)

    proof

      consider e, f such that

       A1: [ [e, f], [f, e]] = [ [a, b], [b, a]];

      

       A2: ((((e `2_3 ) - (f `2_3 )) * ((f `3_3 ) - (e `3_3 ))) - (((f `2_3 ) - (e `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by Lm2;

      ((((e `1_3 ) - (f `1_3 )) * ((f `2_3 ) - (e `2_3 ))) - (((f `1_3 ) - (e `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((f `3_3 ) - (e `3_3 ))) - (((f `1_3 ) - (e `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by Lm2;

      hence thesis by A1, A2, Th12;

    end;

    theorem :: PARSP_1:14

    

     Th14: (a,b) '||' (c,c)

    proof

      consider e, f, g such that

       A1: [ [e, f], [g, g]] = [ [a, b], [c, c]];

      

       A2: ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (g `3_3 ))) - (((g `2_3 ) - (g `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by Lm3;

      ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (g `2_3 ))) - (((g `1_3 ) - (g `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (g `3_3 ))) - (((g `1_3 ) - (g `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by Lm3;

      hence thesis by A1, A2, Th12;

    end;

    theorem :: PARSP_1:15

    

     Th15: (a,b) '||' (p,q) & (a,b) '||' (r,s) implies (p,q) '||' (r,s) or a = b

    proof

      defpred CB[ Element of 3F(F), Element of 3F(F), Element of 3F(F), Element of 3F(F)] means (((($1 `1_3 ) - ($2 `1_3 )) * (($3 `2_3 ) - ($4 `2_3 ))) - ((($3 `1_3 ) - ($4 `1_3 )) * (($1 `2_3 ) - ($2 `2_3 )))) = ( 0. F) & (((($1 `1_3 ) - ($2 `1_3 )) * (($3 `3_3 ) - ($4 `3_3 ))) - ((($3 `1_3 ) - ($4 `1_3 )) * (($1 `3_3 ) - ($2 `3_3 )))) = ( 0. F) & (((($1 `2_3 ) - ($2 `2_3 )) * (($3 `3_3 ) - ($4 `3_3 ))) - ((($3 `2_3 ) - ($4 `2_3 )) * (($1 `3_3 ) - ($2 `3_3 )))) = ( 0. F);

      assume that

       A1: (a,b) '||' (p,q) and

       A2: (a,b) '||' (r,s);

      consider e, f, g, h such that

       A3: [ [e, f], [g, h]] = [ [a, b], [p, q]] and

       A4: CB[e, f, g, h] by A1, Th12;

      consider i, j, k, l such that

       A5: [ [i, j], [k, l]] = [ [a, b], [r, s]] and

       A6: CB[i, j, k, l] by A2, Th12;

      

       A7: i = a & j = b by A5, MCART_1: 93;

      

       A8: k = r & l = s by A5, MCART_1: 93;

      set A = ((e `1_3 ) - (f `1_3 )), B = ((e `2_3 ) - (f `2_3 )), C = ((e `3_3 ) - (f `3_3 )), D = ((g `1_3 ) - (h `1_3 )), E = ((g `2_3 ) - (h `2_3 )), K = ((g `3_3 ) - (h `3_3 )), G = ((k `1_3 ) - (l `1_3 )), H = ((k `2_3 ) - (l `2_3 )), I = ((k `3_3 ) - (l `3_3 ));

      

       A9: e = a & f = b by A3, MCART_1: 93;

      

       A10: g = p & h = q by A3, MCART_1: 93;

      now

        assume

         A11: a <> b;

        now

          

           AA: for X1,X2,X3 be non empty set holds for x be Element of [:X1, X2, X3:] holds x = [(x `1_3 ), (x `2_3 ), (x `3_3 )];

          e = [(e `1_3 ), (e `2_3 ), (e `3_3 )];

          then

           A12: (e `1_3 ) <> (f `1_3 ) or (e `2_3 ) <> (f `2_3 ) or (e `3_3 ) <> (f `3_3 ) by A9, A11, AA;

          per cases by A12, RLVECT_1: 21;

            case

             A13: A <> ( 0. F);

            hence ((D * H) - (G * E)) = ( 0. F) by A4, A6, A9, A7, Lm4;

            thus

             A14: ((D * I) - (G * K)) = ( 0. F) by A4, A6, A9, A7, A13, Lm4;

            (E * I) = (((D * B) * (A " )) * I) & (H * K) = (((G * B) * (A " )) * K) by A4, A6, A9, A7, A13, VECTSP_1: 30;

            hence ((E * I) - (H * K)) = ( 0. F) by A14, Lm8;

          end;

            case

             A15: B <> ( 0. F);

            hence ((D * H) - (G * E)) = ( 0. F) by A4, A6, A9, A7, Lm6;

            thus

             A16: ((E * I) - (H * K)) = ( 0. F) by A4, A6, A9, A7, A15, Lm4;

            (D * I) = (((E * A) * (B " )) * I) & (G * K) = (((H * A) * (B " )) * K) by A4, A6, A9, A7, A15, VECTSP_1: 30;

            hence ((D * I) - (G * K)) = ( 0. F) by A16, Lm8;

          end;

            case

             A17: C <> ( 0. F);

            hence ((E * I) - (H * K)) = ( 0. F) by A4, A6, A9, A7, Lm6;

            

             A18: (D * H) = (((K * A) * (C " )) * H) & (G * E) = (((I * A) * (C " )) * E) by A4, A6, A9, A7, A17, VECTSP_1: 30;

            ((K * H) - (I * E)) = ( 0. F) by A4, A6, A9, A7, A17, Lm6;

            hence ((D * H) - (G * E)) = ( 0. F) by A18, Lm8;

            thus ((D * I) - (G * K)) = ( 0. F) by A4, A6, A9, A7, A17, Lm6;

          end;

        end;

        hence ex g, h, k, l st [ [g, h], [k, l]] = [ [p, q], [r, s]] & CB[g, h, k, l] by A10, A8;

      end;

      hence thesis by Th12;

    end;

    theorem :: PARSP_1:16

    

     Th16: (a,b) '||' (a,c) implies (b,a) '||' (b,c)

    proof

      assume (a,b) '||' (a,c);

      then

      consider e, f, g, h such that

       A1: [ [e, f], [g, h]] = [ [a, b], [a, c]] and

       A2: ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (h `2_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) & ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) and

       A3: ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by Th12;

      

       A4: e = a by A1, MCART_1: 93;

      

       A5: g = a by A1, MCART_1: 93;

      then

       A6: ((((f `2_3 ) - (e `2_3 )) * ((f `3_3 ) - (h `3_3 ))) - (((f `2_3 ) - (h `2_3 )) * ((f `3_3 ) - (e `3_3 )))) = ( 0. F) by A3, A4, Lm13;

      f = b by A1, MCART_1: 93;

      then

       A7: [ [f, e], [f, h]] = [ [b, a], [b, c]] by A1, A4, MCART_1: 93;

      ((((f `1_3 ) - (e `1_3 )) * ((f `2_3 ) - (h `2_3 ))) - (((f `1_3 ) - (h `1_3 )) * ((f `2_3 ) - (e `2_3 )))) = ( 0. F) & ((((f `1_3 ) - (e `1_3 )) * ((f `3_3 ) - (h `3_3 ))) - (((f `1_3 ) - (h `1_3 )) * ((f `3_3 ) - (e `3_3 )))) = ( 0. F) by A2, A4, A5, Lm13;

      hence thesis by A7, A6, Th12;

    end;

    theorem :: PARSP_1:17

    

     Th17: ex d st (a,b) '||' (c,d) & (a,c) '||' (b,d)

    proof

      consider e, f, g such that

       A1: e = a & f = b & g = c;

      set h = ((g + f) + ( - e));

      reconsider d = h as Element of ( MPS F);

      

       A2: [ [e, f], [g, h]] = [ [a, b], [c, d]] by A1;

      take d;

      (g + f) = [((g `1_3 ) + (f `1_3 )), ((g `2_3 ) + (f `2_3 )), ((g `3_3 ) + (f `3_3 ))] & ( - e) = [( - (e `1_3 )), ( - (e `2_3 )), ( - (e `3_3 ))] by Def1, Def3;

      then

       A3: h = [(((g `1_3 ) + (f `1_3 )) + ( - (e `1_3 ))), (((g `2_3 ) + (f `2_3 )) + ( - (e `2_3 ))), (((g `3_3 ) + (f `3_3 )) + ( - (e `3_3 )))] by Th2;

      then

       A4: (h `1_3 ) = (((g `1_3 ) + (f `1_3 )) + ( - (e `1_3 )));

      

       A5: (h `3_3 ) = (((g `3_3 ) + (f `3_3 )) + ( - (e `3_3 ))) by A3;

      then

       A6: ((((e `1_3 ) - (f `1_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by A4, Lm15;

      

       A7: ((((e `1_3 ) - (g `1_3 )) * ((f `3_3 ) - (h `3_3 ))) - (((f `1_3 ) - (h `1_3 )) * ((e `3_3 ) - (g `3_3 )))) = ( 0. F) by A4, A5, Lm15;

      

       A8: (h `2_3 ) = (((g `2_3 ) + (f `2_3 )) + ( - (e `2_3 ))) by A3;

      then

       A9: ((((e `2_3 ) - (f `2_3 )) * ((g `3_3 ) - (h `3_3 ))) - (((g `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (f `3_3 )))) = ( 0. F) by A5, Lm15;

      ((((e `1_3 ) - (f `1_3 )) * ((g `2_3 ) - (h `2_3 ))) - (((g `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (f `2_3 )))) = ( 0. F) by A4, A8, Lm15;

      hence (a,b) '||' (c,d) by A2, A6, A9, Th12;

      

       A10: [ [e, g], [f, h]] = [ [a, c], [b, d]] by A1;

      

       A11: ((((e `2_3 ) - (g `2_3 )) * ((f `3_3 ) - (h `3_3 ))) - (((f `2_3 ) - (h `2_3 )) * ((e `3_3 ) - (g `3_3 )))) = ( 0. F) by A8, A5, Lm15;

      ((((e `1_3 ) - (g `1_3 )) * ((f `2_3 ) - (h `2_3 ))) - (((f `1_3 ) - (h `1_3 )) * ((e `2_3 ) - (g `2_3 )))) = ( 0. F) by A4, A8, Lm15;

      hence thesis by A10, A7, A11, Th12;

    end;

    definition

      let IT be non empty ParStr;

      :: PARSP_1:def12

      attr IT is ParSp-like means

      : Def11: for a,b,c,d,p,q,r,s be Element of IT holds (a,b) '||' (b,a) & (a,b) '||' (c,c) & ((a,b) '||' (p,q) & (a,b) '||' (r,s) implies (p,q) '||' (r,s) or a = b) & ((a,b) '||' (a,c) implies (b,a) '||' (b,c)) & ex x be Element of IT st (a,b) '||' (c,x) & (a,c) '||' (b,x);

    end

    registration

      cluster strict ParSp-like for non empty ParStr;

      existence

      proof

        set F = the Field;

        for a,b,c,d,p,q,r,s be Element of ( MPS F) holds (a,b) '||' (b,a) & (a,b) '||' (c,c) & ((a,b) '||' (p,q) & (a,b) '||' (r,s) implies (p,q) '||' (r,s) or a = b) & ((a,b) '||' (a,c) implies (b,a) '||' (b,c)) & ex x be Element of ( MPS F) st (a,b) '||' (c,x) & (a,c) '||' (b,x) by Th13, Th14, Th15, Th16, Th17;

        then ( MPS F) is ParSp-like;

        hence thesis;

      end;

    end

    definition

      mode ParSp is ParSp-like non empty ParStr;

    end

    reserve PS for ParSp,

a,b,c,d,p,q,r,s for Element of PS;

    theorem :: PARSP_1:18

    

     Th18: (a,b) '||' (a,b)

    proof

      (b,a) '||' (b,b) by Def11;

      hence thesis by Def11;

    end;

    theorem :: PARSP_1:19

    

     Th19: (a,b) '||' (c,d) implies (c,d) '||' (a,b)

    proof

      assume

       A1: (a,b) '||' (c,d);

      (a,b) '||' (a,b) by Th18;

      then a <> b implies (c,d) '||' (a,b) by A1, Def11;

      hence thesis by Def11;

    end;

    theorem :: PARSP_1:20

    

     Th20: (a,a) '||' (b,c)

    proof

      (b,c) '||' (a,a) by Def11;

      hence thesis by Th19;

    end;

    theorem :: PARSP_1:21

    

     Th21: (a,b) '||' (c,d) implies (b,a) '||' (c,d)

    proof

      assume

       A1: (a,b) '||' (c,d);

      (a,b) '||' (b,a) by Def11;

      then a <> b implies (b,a) '||' (c,d) by A1, Def11;

      hence thesis by A1;

    end;

    theorem :: PARSP_1:22

    

     Th22: (a,b) '||' (c,d) implies (a,b) '||' (d,c)

    proof

      assume (a,b) '||' (c,d);

      then (c,d) '||' (a,b) by Th19;

      then (d,c) '||' (a,b) by Th21;

      hence thesis by Th19;

    end;

    theorem :: PARSP_1:23

    

     Th23: (a,b) '||' (c,d) implies (b,a) '||' (c,d) & (a,b) '||' (d,c) & (b,a) '||' (d,c) & (c,d) '||' (a,b) & (d,c) '||' (a,b) & (c,d) '||' (b,a) & (d,c) '||' (b,a)

    proof

      assume (a,b) '||' (c,d);

      then (c,d) '||' (a,b) by Th19;

      then

       A1: (d,c) '||' (a,b) by Th21;

      then

       A2: (d,c) '||' (b,a) by Th22;

      then (c,d) '||' (b,a) by Th21;

      hence thesis by A1, A2, Th19, Th21;

    end;

    theorem :: PARSP_1:24

    

     Th24: (a,b) '||' (a,c) implies (a,c) '||' (a,b) & (b,a) '||' (a,c) & (a,b) '||' (c,a) & (a,c) '||' (b,a) & (b,a) '||' (c,a) & (c,a) '||' (a,b) & (c,a) '||' (b,a) & (b,a) '||' (b,c) & (a,b) '||' (b,c) & (b,a) '||' (c,b) & (b,c) '||' (b,a) & (a,b) '||' (c,b) & (c,b) '||' (b,a) & (b,c) '||' (a,b) & (c,b) '||' (a,b) & (c,a) '||' (c,b) & (a,c) '||' (c,b) & (c,a) '||' (b,c) & (a,c) '||' (b,c) & (c,b) '||' (c,a) & (b,c) '||' (c,a) & (c,b) '||' (a,c) & (b,c) '||' (a,c)

    proof

      assume

       A1: (a,b) '||' (a,c);

      then (a,c) '||' (a,b) by Th19;

      then

       A2: (c,a) '||' (c,b) by Def11;

      (b,a) '||' (b,c) by A1, Def11;

      hence thesis by A1, A2, Th23;

    end;

    theorem :: PARSP_1:25

    a = b or c = d or a = c & b = d or a = d & b = c implies (a,b) '||' (c,d) by Def11, Th18, Th20;

    theorem :: PARSP_1:26

    

     Th26: a <> b & (p,q) '||' (a,b) & (a,b) '||' (r,s) implies (p,q) '||' (r,s)

    proof

      assume that

       A1: a <> b and

       A2: (p,q) '||' (a,b) and

       A3: (a,b) '||' (r,s);

      (a,b) '||' (p,q) by A2, Th23;

      hence thesis by A1, A3, Def11;

    end;

    theorem :: PARSP_1:27

     not (a,b) '||' (a,c) implies a <> b & b <> c & c <> a by Def11, Th18, Th20;

    theorem :: PARSP_1:28

     not (a,b) '||' (c,d) implies a <> b & c <> d by Def11, Th20;

    theorem :: PARSP_1:29

    

     Th29: not (a,b) '||' (a,c) implies not (a,c) '||' (a,b) & not (b,a) '||' (a,c) & not (a,b) '||' (c,a) & not (a,c) '||' (b,a) & not (b,a) '||' (c,a) & not (c,a) '||' (a,b) & not (c,a) '||' (b,a) & not (b,a) '||' (b,c) & not (a,b) '||' (b,c) & not (b,a) '||' (c,b) & not (b,c) '||' (b,a) & not (b,a) '||' (c,b) & not (c,b) '||' (b,a) & not (b,c) '||' (a,b) & not (c,b) '||' (a,b) & not (c,a) '||' (c,b) & not (a,c) '||' (c,b) & not (c,a) '||' (b,c) & not (a,c) '||' (b,c) & not (c,b) '||' (c,a) & not (b,c) '||' (c,a) & not (c,b) '||' (a,c) & not (b,c) '||' (a,c)

    proof

      assume

       A1: not (a,b) '||' (a,c);

      assume not thesis;

      then (a,c) '||' (a,b) or (a,b) '||' (a,c) or (a,b) '||' (a,c) or (a,c) '||' (a,b) or (a,b) '||' (a,c) or (a,c) '||' (a,b) or (a,c) '||' (a,b) or (b,a) '||' (b,c) or (b,a) '||' (b,c) or (b,a) '||' (b,c) or (b,c) '||' (b,a) or (b,a) '||' (b,c) or (b,c) '||' (b,a) or (b,c) '||' (b,a) or (b,c) '||' (b,a) or (c,a) '||' (c,b) or (c,a) '||' (c,b) or (c,a) '||' (c,b) or (c,a) '||' (c,b) or (c,b) '||' (c,a) or (c,b) '||' (c,a) or (c,b) '||' (c,a) or (c,b) '||' (c,a) by Th23;

      hence contradiction by A1, Th24;

    end;

    theorem :: PARSP_1:30

    

     Th30: not (a,b) '||' (c,d) & (a,b) '||' (p,q) & (c,d) '||' (r,s) & p <> q & r <> s implies not (p,q) '||' (r,s)

    proof

      assume that

       A1: not (a,b) '||' (c,d) and

       A2: (a,b) '||' (p,q) and

       A3: (c,d) '||' (r,s) and

       A4: p <> q and

       A5: r <> s;

      assume (p,q) '||' (r,s);

      then (a,b) '||' (r,s) by A2, A4, Th26;

      then

       A6: (r,s) '||' (a,b) by Th23;

      (r,s) '||' (c,d) by A3, Th23;

      hence contradiction by A1, A5, A6, Def11;

    end;

    theorem :: PARSP_1:31

    

     Th31: not (a,b) '||' (a,c) & (a,b) '||' (p,q) & (a,c) '||' (p,r) & (b,c) '||' (q,r) & p <> q implies not (p,q) '||' (p,r)

    proof

      assume that

       A1: not (a,b) '||' (a,c) and

       A2: (a,b) '||' (p,q) and

       A3: (a,c) '||' (p,r) and

       A4: (b,c) '||' (q,r) and

       A5: p <> q;

      now

        assume p = r;

        then

         A6: (p,q) '||' (b,c) by A4, Th23;

        (p,q) '||' (b,a) by A2, Th23;

        then (b,a) '||' (b,c) by A5, A6, Def11;

        hence contradiction by A1, Th24;

      end;

      hence thesis by A1, A2, A3, A5, Th30;

    end;

    theorem :: PARSP_1:32

    

     Th32: not (a,b) '||' (a,c) & (a,c) '||' (p,r) & (b,c) '||' (p,r) implies p = r

    proof

      assume that

       A1: ( not (a,b) '||' (a,c)) & (a,c) '||' (p,r) and

       A2: (b,c) '||' (p,r);

      

       A3: (p,r) '||' (b,c) by A2, Th23;

      ( not (a,c) '||' (b,c)) & (p,r) '||' (a,c) by A1, Th23, Th29;

      hence thesis by A3, Def11;

    end;

    theorem :: PARSP_1:33

    

     Th33: not (p,q) '||' (p,r) & (p,r) '||' (p,s) & (q,r) '||' (q,s) implies r = s

    proof

      assume that

       A1: ( not (p,q) '||' (p,r)) & (p,r) '||' (p,s) and

       A2: (q,r) '||' (q,s);

      

       A3: (r,s) '||' (r,q) by A2, Th29;

      ( not (r,p) '||' (r,q)) & (r,s) '||' (r,p) by A1, Th29;

      hence thesis by A3, Def11;

    end;

    theorem :: PARSP_1:34

     not (a,b) '||' (a,c) & (a,b) '||' (p,q) & (a,c) '||' (p,r) & (a,c) '||' (p,s) & (b,c) '||' (q,r) & (b,c) '||' (q,s) implies r = s

    proof

      assume that

       A1: not (a,b) '||' (a,c) and

       A2: (a,b) '||' (p,q) and

       A3: (a,c) '||' (p,r) and

       A4: (a,c) '||' (p,s) and

       A5: (b,c) '||' (q,r) and

       A6: (b,c) '||' (q,s);

       A7:

      now

        b <> c by A1, Th18;

        then

         A8: (q,r) '||' (q,s) by A5, A6, Def11;

        a <> c by A1, Def11;

        then

         A9: (p,r) '||' (p,s) by A3, A4, Def11;

        assume p <> q;

        then not (p,q) '||' (p,r) by A1, A2, A3, A5, Th31;

        hence thesis by A9, A8, Th33;

      end;

      p = q implies p = r & p = s by A1, A3, A4, A5, A6, Th32;

      hence thesis by A7;

    end;

    theorem :: PARSP_1:35

    

     Th35: (a,b) '||' (a,c) & (a,b) '||' (a,d) implies (a,b) '||' (c,d)

    proof

      assume that

       A1: (a,b) '||' (a,c) and

       A2: (a,b) '||' (a,d);

      now

        assume that

         A3: a <> b and

         A4: a <> c;

        (a,c) '||' (a,d) by A1, A2, A3, Def11;

        then (a,c) '||' (c,d) by Th24;

        hence thesis by A1, A4, Th26;

      end;

      hence thesis by A2, Th20;

    end;

    theorem :: PARSP_1:36

    (for a, b holds a = b) implies for p, q, r, s holds (p,q) '||' (r,s)

    proof

      assume

       A1: for a, b holds a = b;

      let p, q, r, s;

      r = s by A1;

      hence thesis by Def11;

    end;

    theorem :: PARSP_1:37

    (ex a, b st a <> b & for c holds (a,b) '||' (a,c)) implies for p, q, r, s holds (p,q) '||' (r,s)

    proof

      assume ex a, b st a <> b & for c holds (a,b) '||' (a,c);

      then

      consider a, b such that

       A1: a <> b and

       A2: for c holds (a,b) '||' (a,c);

      let p, q, r, s;

      (a,b) '||' (a,r) & (a,b) '||' (a,s) by A2;

      then

       A3: (a,b) '||' (r,s) by Th35;

      (a,b) '||' (a,p) & (a,b) '||' (a,q) by A2;

      then (a,b) '||' (p,q) by Th35;

      hence thesis by A1, A3, Def11;

    end;

    theorem :: PARSP_1:38

     not (a,b) '||' (a,c) & p <> q implies not (p,q) '||' (p,a) or not (p,q) '||' (p,b) or not (p,q) '||' (p,c)

    proof

      assume that

       A1: not (a,b) '||' (a,c) and

       A2: p <> q;

      assume

       A3: not thesis;

      then (p,a) '||' (p,b) by A2, Def11;

      then

       A4: (a,p) '||' (a,b) by Th24;

      (p,a) '||' (p,c) by A2, A3, Def11;

      then

       A5: (a,p) '||' (a,c) by Th24;

      a <> p by A1, A2, A3, Def11;

      hence contradiction by A1, A4, A5, Def11;

    end;