# Help with an integral

Hi there!
I have to calculate the integral of the function sqrt(x^2+y^2) over the circle (x-1)^2+y^2<=1

I use polar coordinates: rho goes from 0 to 2cos(theta) and theta goes from 0 to 2pi.
My result is that the integral is 0... is it right?

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Yea I did it and got 0 because you end up integrating $\cos(\theta)^3$ at the end, which is 0.

eohgan, if you think about what the geometric meaning of the integral is, it should be clear as to why your answer is zero.

tiny-tim
Homework Helper
Hi there!
I have to calculate the integral of the function sqrt(x^2+y^2) over the circle (x-1)^2+y^2<=1

I use polar coordinates: rho goes from 0 to 2cos(theta) and theta goes from 0 to 2pi.
My result is that the integral is 0... is it right?
Hi eoghan!

erm … doesn't theta go from -π/2 to π/2?