I'd like to know where I went wrong :
A lattice with constant density is on the region under the curve from to . Find the moments of inertia and .
My attempt : :
I realize that the region is an upper semi circle with radius .
, which mean that does not depend on the mass of the lattice!
I'm guessing that my error comes from the first step, that is . Should I replace by , so ?
If so, then I don't understand why I can't take as ...