Does anyone know a good sight that explains, step-by-step, how to derive unit vectors in spherical coordinates? I am at that unfortunate place where I have been looking at it for so long I know the answer from sheer memorization, but don't understand the derivation. From the definitions I am looking at, each unit vector is a derivative of the vector r wrt the unit vector in question divided by the absolute value of the same derivative (as described at http://mathworld.wolfram.com/SphericalCoordinates.html). It is the denominator that is throwing me off. Can anyone help before I lose my mind? Thanks!