1. The problem statement, all variables and given/known data Solve: ∫(-ydx+xdy)/(x2+y2) counterclockwise around x2+y2=4 2. Relevant equations Greens Theorem: ∫Pdx + Qdy = ∫∫(dQ/dx - dP/dy)dxdy 3. The attempt at a solution Using Greens Theorem variables, I get that: P = -y/(x2+y2) and Q=x/(x2+y2) and thus dQ/dx = (y2-x2)/(y2+x2)2 and dP/dx = (y2-x2)/(y2+x2)2 So, ∫∫(dQ/dx - dP/dy)dxdy = ∫∫( (y2-x2)/(y2+x2)2 - (y2-x2)/(y2+x2)2)dxdy ... which means I'm integrating 0 (which can't be right as that would equal 0 over a definite integral). Not sure where I've gone wrong! Can anyone spot an error?