Simplification of arctan2(f1,f2) expressions.
Why doesn't arctan2(sqrt(a^2 + r^2)*sin(phi)*sin(th), sqrt(a^2 + r^2)*cos(phi)*sin(th)) simplify to phi or at least arctan2(sin(phi),cos(phi))?
Why should it ?
I was working out transformations between coordinate systems. As a test I transformed and then untransformed so there should be no change. However I get this term which won't simplify back to phi.