P(A∩B)=P(A)P(B∣A)P(A \cap B) = P(A) P(B|A)P(A∩B)=P(A)P(B∣A); independent iff P(A∩B)=P(A)P(B)P(A \cap B) = P(A) P(B)P(A∩B)=P(A)P(B).