Finding the potential.
general solution of potential is in terms of spherical harmonics Y_l,m.
The Attempt at a Solution
My question is how do we know which l to choose given a boundry condition. for example if the potenial on the surface of a sphere of radius "a" = const*sin (theta) cos(theta). How do we know which l that corresonds to? or do we try all the l's and see which one works out?