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- 0

## Homework Statement

[tex]I=\int^{a}_{0}dx\int^{\sqrt{a^{2}-x^{2}}_{0}[/tex][tex](x-y)dy[/tex]

## Homework Equations

[tex]r^{2}=x^{2}+y^{2}[/tex]

## The Attempt at a Solution

Im thinking that the question is asking to integrate the first quarter of the circle of radius a between 0 and pi/2. In that case ive changed the limits to :-

[tex]\int^{\frac{\pi}{2}}_{0}\int^{a}_{0}r.dr.d\theta[/tex] but now im not sure what to do with the (x-y) given in the question. I cant seem to be able to rearrange this - [tex]r^{2}=x^{2}+y^{2}[/tex] to give me a value i can use in polar coordinates.

This integral apparantly is supposed to give an answer of 0. is this correct? i don't see how it can be zero if there is a limit of a.