Now if I have (the Bessel equation):
(\frac{\partial^2}{\partial r^2}+\frac{1}{r}\frac{\partial}{\partial r}+(\lambda^2 -n^2\frac{1}{r^2})u_{k,m}(r,\phi)=0, (0<r<b,0<=\phi<=2\pi)
\phi_{k,m}(r,\phi)=0, (r=b, 0<=\phi<=2\pi)
The solution would be:
u_{k,m}(r,\phi)=AJ_n(\lambda r)+BY_n(\lambda r)...