# Applying Green's Theorem 3

When using green's theorem to evaluate a line integral $$\oint_C P\;dx + Q\;dy = \iint_D \left(\frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y}\right)\;dx\,dy$$ where $C$ is a circle, I know we have to use the cylindrical coordinates $(r,\theta,z)$. My question is how do we change the $dx\,dy$ on the right hand side of the equation to $r\,dr\,d\theta$.

• – jm324354 May 3 '15 at 18:29
• I appreciate it, thank you – Kenneth May 3 '15 at 18:32