let A, B, C, D, E, F be set ; :: thesis: for h being Function
for A', B', C', D', E', F' being set st A <> B & A <> C & A <> D & A <> E & A <> F & B <> C & B <> D & B <> E & B <> F & C <> D & C <> E & C <> F & D <> E & D <> F & E <> F & h = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) +* (A .--> A') holds
( h . A = A' & h . B = B' & h . C = C' & h . D = D' & h . E = E' & h . F = F' )
let h be Function; :: thesis: for A', B', C', D', E', F' being set st A <> B & A <> C & A <> D & A <> E & A <> F & B <> C & B <> D & B <> E & B <> F & C <> D & C <> E & C <> F & D <> E & D <> F & E <> F & h = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) +* (A .--> A') holds
( h . A = A' & h . B = B' & h . C = C' & h . D = D' & h . E = E' & h . F = F' )
let A', B', C', D', E', F' be set ; :: thesis: ( A <> B & A <> C & A <> D & A <> E & A <> F & B <> C & B <> D & B <> E & B <> F & C <> D & C <> E & C <> F & D <> E & D <> F & E <> F & h = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) +* (A .--> A') implies ( h . A = A' & h . B = B' & h . C = C' & h . D = D' & h . E = E' & h . F = F' ) )
assume A1: ( A <> B & A <> C & A <> D & A <> E & A <> F & B <> C & B <> D & B <> E & B <> F & C <> D & C <> E & C <> F & D <> E & D <> F & E <> F & h = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) +* (A .--> A') ) ; :: thesis: ( h . A = A' & h . B = B' & h . C = C' & h . D = D' & h . E = E' & h . F = F' )
A2: dom (A .--> A') = {A} by FUNCOP_1:19;
A3: h . A = A'

proof

A in dom (A .--> A') by A2, TARSKI:def 1;
then h . A = (A .--> A') . A by A1, FUNCT_4:14;
hence h . A = A' by FUNCOP_1:87; :: thesis: verum

end;

A4: h . B = B'

proof

not B in dom (A .--> A') by A1, A2, TARSKI:def 1;
then h . B = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) . B by A1, FUNCT_4:12
.= B' by A1, Th29 ;
hence h . B = B' ; :: thesis: verum

end;

A5: h . C = C'

proof

not C in dom (A .--> A') by A1, A2, TARSKI:def 1;
then h . C = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) . C by A1, FUNCT_4:12;
hence h . C = C' by A1, Th29; :: thesis: verum

end;

A6: h . D = D'

proof

not D in dom (A .--> A') by A1, A2, TARSKI:def 1;
then h . D = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) . D by A1, FUNCT_4:12
.= D' by A1, Th29 ;
hence h . D = D' ; :: thesis: verum

end;

A7: h . E = E'

proof

not E in dom (A .--> A') by A1, A2, TARSKI:def 1;
then h . E = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) . E by A1, FUNCT_4:12
.= E' by A1, Th29 ;
hence h . E = E' ; :: thesis: verum

end;

h . F = F'

proof

not F in dom (A .--> A') by A1, A2, TARSKI:def 1;
then h . F = (((((B .--> B') +* (C .--> C')) +* (D .--> D')) +* (E .--> E')) +* (F .--> F')) . F by A1, FUNCT_4:12
.= F' by A1, Th29 ;
hence h . F = F' ; :: thesis: verum

end;

hence ( h . A = A' & h . B = B' & h . C = C' & h . D = D' & h . E = E' & h . F = F' ) by A3, A4, A5, A6, A7; :: thesis: verum