part where we are having Z this would be Z equals Z we need to keep it consistently to that part we can sometimes have it sometimes not when we do this but then same thing with Bayes rule yeah initially it was for the full rectangle now we restricted attention to some sub region no problem we just condition everywhere P X given Y comma Z is equal to let's it's equal to well what do we have we had Y given X but of course also Z because Z needs to be in the back everywhere now then P X but we need to carry along the Z and then normalize by