1. The problem statement, all variables and given/known data A sphere of radius R, centered at the origin, carries charge density ρ(r,θ) = (kR/r2)(R - 2r)sinθ, where k is a constant, and r, θ are the usual spherical coordinates. Find the approximate potential for points on the z axis, far from the sphere. 2. Relevant equations potential of the dipole V(r,θ) = 1/4πεo * 1/r2 ∫ r'cosθ' ρ(r') dτ' 3. The attempt at a solution I just want to know why I'm giving the charge density in terms of r and θ and yet I need it in terms of r'. I know that the vector r' is related to θ' by r' = rcosθ' So I tried to say that since θ is the inclination from the xy plane and θ' is the angle between r and r' so that θ'+θ = π/2. Then that would give me sinθ = [(π/2))-θ'] = cosθ' Since the direction of r' is cosθ' I thought maybe I could replace r with r'? so maybe ρ(r',θ') = (kR/r'2)(R - 2r')cosθ' so ρ(r') = (kR/r'2)(R - 2r') ????? PLEASE help I have a test on this tomorrow..