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> Let $D$ be the region bounded by $x+y = 1$, $x= 0$, $y = 0$. Use the result of [Exercise 19](https://i.imgur.com/8ODGDJ7.png) to show that $$\iint\_D\cos\bigg(\frac{x-y}{x+y}\bigg)~dx~dy = \frac{\sin 1}{2} $$
>  and graph $D$ on an $xy$ plane and a $uv$ plane, with $u = x-y$ and $v = x+y$.
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I got the Jacobian determinant is $\dfrac{1}{2}$, but how do I get the limits of integration for $u$ and $v$?