[SOLVED] Evaluating line integrals 1. The problem statement, all variables and given/known data I am given a line integral: [tex]\int (x^2+y^2)^2ds[/tex], where C is a circle of radius 3 with centre in (0;0). Evaluate it. 3. The attempt at a solution Ok, first I know [tex](x^2+y^2)^2[/tex] = [tex]81[/tex]. So far, so good. Then I know for an object in the xy-plane, ds = r*dr*d[tex]\theta[/tex]. I just insert and use the correct limits, and do the integral? Thanks in advance.