let ap, bp, cp, dp be non pair set ; :: thesis: for cin being set
for s being State of (BitFTA0Circ (ap,bp,cp,dp,cin))
for a123, a5 being Element of BOOLEAN st a123 = s . (GFA0AdderOutput (ap,bp,cp)) & a5 = s . cin holds
(Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = a123 'xor' a5

let cin be set ; :: thesis: for s being State of (BitFTA0Circ (ap,bp,cp,dp,cin))
for a123, a5 being Element of BOOLEAN st a123 = s . (GFA0AdderOutput (ap,bp,cp)) & a5 = s . cin holds
(Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = a123 'xor' a5

set S = BitFTA0Str (ap,bp,cp,dp,cin);
set C = BitFTA0Circ (ap,bp,cp,dp,cin);
set A1 = GFA0AdderOutput (ap,bp,cp);
set A1cin = [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2];
let s be State of (BitFTA0Circ (ap,bp,cp,dp,cin)); :: thesis: for a123, a5 being Element of BOOLEAN st a123 = s . (GFA0AdderOutput (ap,bp,cp)) & a5 = s . cin holds
(Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = a123 'xor' a5

let a123, a5 be Element of BOOLEAN ; :: thesis: ( a123 = s . (GFA0AdderOutput (ap,bp,cp)) & a5 = s . cin implies (Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = a123 'xor' a5 )
assume A1: ( a123 = s . (GFA0AdderOutput (ap,bp,cp)) & a5 = s . cin ) ; :: thesis: (Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = a123 'xor' a5
A2: dom s = the carrier of (BitFTA0Str (ap,bp,cp,dp,cin)) by CIRCUIT1:3;
A3: ( GFA0AdderOutput (ap,bp,cp) in the carrier of (BitFTA0Str (ap,bp,cp,dp,cin)) & cin in the carrier of (BitFTA0Str (ap,bp,cp,dp,cin)) ) by Th4;
InnerVertices (BitFTA0Str (ap,bp,cp,dp,cin)) = the carrier' of (BitFTA0Str (ap,bp,cp,dp,cin)) by FACIRC_1:37;
then [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] in the carrier' of (BitFTA0Str (ap,bp,cp,dp,cin)) by Th5;
hence (Following s) . [<*(GFA0AdderOutput (ap,bp,cp)),cin*>,xor2] = xor2 . (s * <*(GFA0AdderOutput (ap,bp,cp)),cin*>) by FACIRC_1:35
.= xor2 . <*a123,a5*> by A1, A3, A2, FINSEQ_2:125
.= a123 'xor' a5 by FACIRC_1:def 4 ;
:: thesis: verum