this yes Suroosh actually when you use the mic so you talked about the normalization at the very end is that trivial every in every instance or are there certain instances in which you can't do it analytically or it's computationally intractable yeah so I would say there's even a more general question as we look at these update equations for filter and smoother are they tractable in general and in general they are not and we'll actually see approximations later this lecture where we it's not tractable because they're