1. The problem statement, all variables and given/known data http://docs.google.com/Doc?id=d277r7r_60c2235gfg 2. Relevant equations [tex] M(Rcm)=\int(rdm) [/tex] 3. The attempt at a solution Okay, so I've figured out that I have to integrate the radii by the mass element dm, which in this case would be p, because that's the mass/unit area? I think that's right, but even there I'm not sure and the actual integral itself I have no idea how to do for such a weird shape.