1. Nov 26, 2012

### Chromosom

1. The problem statement, all variables and given/known data

Compute work: $$\vec{F}=[\sin y,\sin x]$$ on bound: $$\partial D\colon 0\le y\le x$$ and $$x^2+y^2\le1$$.

3. The attempt at a solution

I have been working with integrals for many years, but this exercise was problematic for me because of the following integral:

$$\iint\limits_D(\cos x-\cos y)\,\text dx\,\text dy$$

I tried polar coordinations, but it follows to $$\cos(r\sin\theta)$$ and similar functions. Is there any easy way to solve it?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution