Q: Show that is equal to for every circle centered at .

First, I wrote

Now,

.

So,

.

Thus,

Here is where I am stuck. Firstly, I am assuming I will need to use the parameterization , , with .

So, I want to integrate along x-x_{0})^{2}+(y-y_{0})^{2}=r\}" alt="C=\{(x,y)x-x_{0})^{2}+(y-y_{0})^{2}=r\}" />. I am not sure how to use the parameters and integrate along this curve.

Any help would be appreciated.

Thanks