let x, y, c be set ; :: thesis: ( x <> [<*y,c*>,'&'] & y <> [<*c,x*>,'&'] & c <> [<*x,y*>,'&'] & c <> [<*x,y*>,'xor'] implies for s being State of (BitAdderWithOverflowCirc (x,y,c))
for a1, a2, a3 being Element of BOOLEAN st a1 = s . x & a2 = s . y & a3 = s . c holds
( (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 & (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) ) )

assume that
A1: x <> [<*y,c*>,'&'] and
A2: y <> [<*c,x*>,'&'] and
A3: c <> [<*x,y*>,'&'] and
A4: c <> [<*x,y*>,'xor'] ; :: thesis: for s being State of (BitAdderWithOverflowCirc (x,y,c))
for a1, a2, a3 being Element of BOOLEAN st a1 = s . x & a2 = s . y & a3 = s . c holds
( (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 & (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) )

set f = 'xor' ;
set S1 = 2GatesCircStr (x,y,c,'xor');
set S2 = MajorityStr (x,y,c);
set A = BitAdderWithOverflowCirc (x,y,c);
set A1 = BitAdderCirc (x,y,c);
set A2 = MajorityCirc (x,y,c);
let s be State of (BitAdderWithOverflowCirc (x,y,c)); :: thesis: for a1, a2, a3 being Element of BOOLEAN st a1 = s . x & a2 = s . y & a3 = s . c holds
( (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 & (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) )

let a1, a2, a3 be Element of BOOLEAN ; :: thesis: ( a1 = s . x & a2 = s . y & a3 = s . c implies ( (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 & (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) ) )
assume that
A5: a1 = s . x and
A6: a2 = s . y and
A7: a3 = s . c ; :: thesis: ( (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 & (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) )
A8: x in the carrier of (2GatesCircStr (x,y,c,'xor')) by FACIRC_1:60;
A9: y in the carrier of (2GatesCircStr (x,y,c,'xor')) by FACIRC_1:60;
A10: c in the carrier of (2GatesCircStr (x,y,c,'xor')) by FACIRC_1:60;
A11: x in the carrier of (MajorityStr (x,y,c)) by FACIRC_1:72;
A12: y in the carrier of (MajorityStr (x,y,c)) by FACIRC_1:72;
A13: c in the carrier of (MajorityStr (x,y,c)) by FACIRC_1:72;
reconsider s1 = s | the carrier of (2GatesCircStr (x,y,c,'xor')) as State of (BitAdderCirc (x,y,c)) by FACIRC_1:26;
reconsider s2 = s | the carrier of (MajorityStr (x,y,c)) as State of (MajorityCirc (x,y,c)) by FACIRC_1:26;
reconsider t = s as State of ((BitAdderCirc (x,y,c)) +* (MajorityCirc (x,y,c))) ;
InputVertices (2GatesCircStr (x,y,c,'xor')) = {x,y,c} by A4, FACIRC_1:57;
then A14: InputVertices (2GatesCircStr (x,y,c,'xor')) = InputVertices (MajorityStr (x,y,c)) by A1, A2, A3, Th20;
A15: InnerVertices (2GatesCircStr (x,y,c,'xor')) misses InputVertices (2GatesCircStr (x,y,c,'xor')) by XBOOLE_1:79;
A16: InnerVertices (MajorityStr (x,y,c)) misses InputVertices (MajorityStr (x,y,c)) by XBOOLE_1:79;
A17: dom s1 = the carrier of (2GatesCircStr (x,y,c,'xor')) by CIRCUIT1:3;
then A18: a1 = s1 . x by A5, A8, FUNCT_1:47;
A19: a2 = s1 . y by A6, A9, A17, FUNCT_1:47;
A20: a3 = s1 . c by A7, A10, A17, FUNCT_1:47;
(Following (t,2)) . (2GatesCircOutput (x,y,c,'xor')) = (Following (s1,2)) . (2GatesCircOutput (x,y,c,'xor')) by A14, A16, FACIRC_1:32;
hence (Following (s,2)) . (BitAdderOutput (x,y,c)) = (a1 'xor' a2) 'xor' a3 by A4, A18, A19, A20, FACIRC_1:64; :: thesis: (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1)
A21: dom s2 = the carrier of (MajorityStr (x,y,c)) by CIRCUIT1:3;
then A22: a1 = s2 . x by A5, A11, FUNCT_1:47;
A23: a2 = s2 . y by A6, A12, A21, FUNCT_1:47;
A24: a3 = s2 . c by A7, A13, A21, FUNCT_1:47;
(Following (t,2)) . (MajorityOutput (x,y,c)) = (Following (s2,2)) . (MajorityOutput (x,y,c)) by A14, A15, FACIRC_1:33;
hence (Following (s,2)) . (MajorityOutput (x,y,c)) = ((a1 '&' a2) 'or' (a2 '&' a3)) 'or' (a3 '&' a1) by A1, A2, A3, A22, A23, A24, Lm4; :: thesis: verum