While reading along the probabilistic robotics book, I came across these set of equations which bothers me. Let's take equation 2.13 for example.
P(Y) was expressed into a summation referred to as law of total probability. But should it be conditioned to x' only? Does not the law of total probability state?
P(Y) = P(Y,X) + P(Y,X')
Then why is it only conditioned to x'?