How come I get a negative answer?
What's wrong?
10x in advance.
New questions require new threads.
You need to switch to a new set of coordinates. The integrand suggests the following transformation:
.... (1)
.... (2)
(1) and (2) imply and .
Jacobian of the transformation: .
The region of integration in the xy-plane transforms into the region in the uv-plane bounded by the lines and .
So the integral becomes .