1. The problem statement, all variables and given/known data I am currently trying to calculate the moment and products of inertia of a ring rotating about the x axis at the moment the ring lies in the xy plane. The problem is that the notations I have from textbook are denoted for Cartesian coordinates. i.e. Ixx=∑i mi(yi2+zi2), and Ixy=∑imixiyi. How can I convert these to polar coordinates? 2. Relevant equations x=rcosθ, y=rsinθ, z=? 3. The attempt at a solution I'd assume that the moment of inertia would become Ixx=∑mr2dθ. but since the problem is for a ring with linear mass density, I am also wondering must I exclude certain coordinates? thank you in advance.