# Thread: Find integral of polar function h(r,theta) = rcos(theta) over a circle

1. ## Find integral of polar function h(r,theta) = rcos(theta) over a circle

Hello,

I am studying for my math final and our prof gave us a review but without any solutions or hints. I don't really understand this problem so if anyone could help me out here I would appreciate it.

Question: Find the integral of the polar function h(r, theta) = r cos(theta) , r >= 0, over
the circle r = 2a cos(theta) .

Again I would appreciate the help.

2. ## Re: Find integral of polar function h(r,theta) = rcos(theta) over a circle

Hey lytwynk.

Are you integrating a double integral over the region that is bounded by a circle with radius 2*a with centre (0,0) or are you integrating a line integral with the boundary equal to that same circle?

3. ## Re: Find integral of polar function h(r,theta) = rcos(theta) over a circle

To be honest I am not sure. The question was written word for word. Just any insight into what I should do would be helpful.
Thanks

4. ## Re: Find integral of polar function h(r,theta) = rcos(theta) over a circle

I'm going to assume its over a 2D region defined by a circle since r >= 0.

Hint: With regards to your limits the integral will have r going from 0 to 2a and theta going from 0 to 2*pi.

5. ## Re: Find integral of polar function h(r,theta) = rcos(theta) over a circle

OK, I think I got it now. Thanks for the help.