1. The problem statement, all variables and given/known data So if you integrate over a spherical area, say a ball of radius 1, then 0≤p≤1, 0≤θ≤2∏, and 0≤∅≤∏. My question is why don't you integrate ∅ between 0 and 2∏? I mean if you are integrating over a sphere then you have to go around it vertically AND horizontally completely? wouldn't both the angles be from 0 to 2∏? Thanks genius's :D edit: does it have something to do with the fact that you add a p^2sin(phi) when integrating in spherical coordinates?