# Math Help - Probability Proof Question

1. ## Probability Proof Question

IF A=B with probability 1 then P(A) = P(B)=P(AB)

should this be solved as using addition law as follows ...

P (A B) = P (A) + P (B) = 1

i am not sure ... does anyone have any input?

2. This is how I see it:

P(AB)=P(A¬B).P(B) but P(A¬B)=1 as A=B with probability one
=> P(AB)=P(B)
Analogously, P(AB)=P(B¬A)P(A) => P(AB)=P(A)
"¬" denotes conditional probability(sorry don't know how to use latex)