1. The problem statement, all variables and given/known data Evaluate the integral (x^2+y^2)arctan(y/x) for 0<y<a and 0<x<(a^2-y^2)^0.5. 2. Relevant equations 3. The attempt at a solution I tried changing the order of integration to get the integral (x^2+y^2)arctan(y/x) for 0<x<a and 0<y<(a^2-x^2)^0.5. I noticed that this was a quarter of a circle. I tried then taking x^2 out of the dy integral and into the dx one. The dy integral is then (1+(y/x)^2)arctan(y/x). I'm not sure what to do now.