Thanks Denny. Yesterday, I solve it in a simple way for my notes. I also saw Byron's book, and it's a nice way to solve it. Thanks again anyway, hope this thread helps some other lost soul.
Denny sorry for my late answer. I just came back from a long holiday. The green's function proof was in several books. One I can remember was Fundamentals of Mathematical Physics by Edgar Kraut. My problem with those proofs is that they propose a magical expansion from nowhere (which is ok), but...
Ok I'll write it down. I need to prove:
\frac{e^{-ikR}}{R}=\sum [(2n+1)j_{n}(kb)h_{n}(kr)P_{n}(cos \theta)]
where:
R=\sqrt{r^2+b^2-2brcos(\theta)} and the sum goes from zero to infinity over n.
I know it's a particular case of gegenbauer addition theorem. I understand what it means. I...
I really need to prove eq. 10.1.45 and 10.1.46 of Abramowitz and Stegun Handbook on Mathematical functions. Is an expansion of e^(aR)/R in terms of Special Functions! Any help will be appreciated.