1. The problem statement, all variables and given/known data Evaluate the integral ∫∫dΩ V(Ω)Yml(Ω) for V(Ω) = +V0 for 0<θ<π/2 ; -V0 for π/2<θ<π 2. Relevant equations I was hoping to apply the orthonormality properties of the spherical harmonics but this is a little more difficult since the integral breaks into two integrals over half spheres instead of one integral over a full sphere. I guess it may be useful to rewrite the V(Ω) as ±√(4π)Y00(Ω)V0 in order to invoke the orthogonality properties of the spherical harmonics when integrated on a sphere. 3. The attempt at a solution Basically I've split the integral into two integrals over the upper and lower halves of the sphere. Now what? Surely I'm not to use the definition of the spherical harmonics; there must be a cleaner way to do this by invoking the properties of Ylm(omega). There is nothing I can say about ∫∫half of spheredΩYlm(Y00)* as far as I know. Is there some way to combine the two integrals again so that I can use the orthonormality property?