:: deftheorem ProbSumDef defines probsum_conorm FUZNORM1:def 9 :
for b₁ being BinOp of [.0,1.] holds
( b₁ = probsum_conorm iff for a, b being Element of [.0,1.] holds b₁ . (a,b) = (a + b) - (a * b) );