theorem :: TWOSCOMP:3

for x, y being Element of BOOLEAN holds
( or2 . <*x,y*> = x 'or' y & or2a . <*x,y*> = ('not' x) 'or' y & nand2 . <*x,y*> = ('not' x) 'or' ('not' y) ) by FACIRC_1:def 5, Def4, Lm2;