:: deftheorem Def3 defines ++ FUZZY_2:def 3 :
for C being non empty set
for h, g, b₄ being Membership_Func of C holds
( b₄ = h ++ g iff for c being Element of C holds b₄ . c = ((h . c) + (g . c)) - ((h . c) * (g . c)) );