theorem :: FSCIRC_1:12

for x, y, c being non pair set
for s being State of (BorrowCirc (x,y,c))
for a1, a3 being Element of BOOLEAN st a1 = s . x & a3 = s . c holds
(Following s) . [<*x,c*>,and2a] = ('not' a1) '&' a3