let x, y, c be non pair set ; :: thesis: for s being State of (BorrowCirc (x,y,c))
for a1, a2 being Element of BOOLEAN st a1 = s . x & a2 = s . y holds
(Following (s,2)) . [<*x,y*>,and2a] = ('not' a1) '&' a2
reconsider a = c as Vertex of (BorrowStr (x,y,c)) by Th6;
let s be State of (BorrowCirc (x,y,c)); :: thesis: for a1, a2 being Element of BOOLEAN st a1 = s . x & a2 = s . y holds
(Following (s,2)) . [<*x,y*>,and2a] = ('not' a1) '&' a2
s . a is Element of BOOLEAN ;
hence for a1, a2 being Element of BOOLEAN st a1 = s . x & a2 = s . y holds
(Following (s,2)) . [<*x,y*>,and2a] = ('not' a1) '&' a2 by Lm2; :: thesis: verum