# Deriving the divergence in polar coordinates

1. Oct 16, 2009

### Amok

1. The problem statement, all variables and given/known data

I want to find the divergence operator in polar coordinates (theta and r). I know how to write this operator in cartesian coordinates.

3. The attempt at a solution

I let F(F1,F2) be a vector field. I calculated the partial derivatives of F1 and F2 with respect to x and y respectively ( I said F1 and F2 were functions of theta and r and used the chain rule). That was easy, but I don't get the right answer. I'm pretty sure the reason I got it wrong has something to do with the fact that I didn't take into account the unit vectors in polar coordinates.

Could anyone show me how it's done or at least explain to me what I should do? I would've written more equations, but I don't really know how to do this. I hope it's clear.