I am having problem with an integral. I dont know how to write in mathcode so excuse me for my notation. This is in spherical coordinates: x = theta y = psi r = radial component the integrand is: (cos(x)/r^2) I want to integrate this over a solid angle of an arbitrary surface. da is a differential area. And in spherical coordiantes should be: da = r^2*sin(x)dxdy I know the integral should be 4*pi but I dont get it right. I want to have the antiderivate as (cos(x)^2)/2 from 0 to pi. Then I get 1/2*2pi = pi So I am missing a factor 4 here. Can anyone help me show what I've missed?