1. The problem statement, all variables and given/known data I have to prove the divergence formula for plane polars. The question goes something like: Find the divergence of the vector field F(r,t) = Frer + Ftet where r and t are polar coordinates and er = (cos t, sin t, 0) and et = (- sin t, cos t, 0) (t is theta in the question but t was easier to type) 2. Relevant equations x=rcost y=rsint Divergence formula in cartesian coordinates 3. The attempt at a solution F(r,t) = (Frcost - Ftsint, Frsint + Ftcost, 0) Could I partially differentiate the first bit with respect to r and the second bit with respect to t, just ignoring the 0 at the end? This does not seem right, I'm not sure if it is even possible. Or I feel like the chain rule might come into it somewhere? I really don't know where to start.