It's unfortunate the first equation was mistyped, one way to check is that the Bayes's rule can be derived from a rule in conditional probability: P(A,B) = P(B

It's unfortunate the first equation was mistyped, one way to check is that the Bayes's rule can be derived from a rule in conditional probability: P(A,B) = P(B,A) P(A|B) * P(B) = P(B|A) * P(A) The formulation in the blog post would say instead: P(A|B) * P(A) = P(B|A) * P(B) which does not really make sense.