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, Th21;
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 CIRCUIT1:4;
then A18: a1 = s1 . x by A5, A8, FUNCT_1:70;
A19: a2 = s1 . y by A6, A9, A17, FUNCT_1:70;
A20: a3 = s1 . c by A7, A10, A17, FUNCT_1:70;
(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 CIRCUIT1:4;
then A22: a1 = s2 . x by A5, A11, FUNCT_1:70;
A23: a2 = s2 . y by A6, A12, A21, FUNCT_1:70;
A24: a3 = s2 . c by A7, A13, A21, FUNCT_1:70;
(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