Several people have asked me about POTW #2 part (b). I should clarify the response I made on the newsgroup a few days ago. I imagine that Dr. Bovik meant the ROC to be |z|>1, and that's what you should use.

I have also been asked about part (c). When he says you cannot make use of any other Fourier transforms or properties, that precludes you from (for instance) looking up the F.T. of u(n) in a table, then modulating this with cos(pi*n) and using the modulation property to get the answer. (Well, I just gave you the way to check your working.) You MUST do the transform directly. That means make use of the part in the notes where the F.T. of u(n) is derived, and do something similar!

Tom