I've been working on a plane wave expansion in spherical harmonics.. as demonstrated in Bohren and Huffman (if anyone's familiar with it_)... I have more or less finished my code in Matlab and I'm putting in values to expand and compare with the exact solution... in short, i'm having trouble when defining some of my components as zero... getting results going crazy all over the place.!! now I appreciate this would seem like a problem with the code but looking at the equations in Bohren and Huffman(4.19) (and in my code) there seems to be a different problem!.. one of the terms is divisible by a sin(m*phi) value and of course this value is going to go to zero with my phi and then the term goes to infinity!!! so my result ends up being nonsensical..> if anyone is familiar with the field t'would be nice to hear!