Question

how will u derive the center of gravity of the solid cone

Answer 1

integral calculus.

if you are not yet doing calculus, i suspect there are geometric proofs, though that is not something i would know off the top of my head....

if you are doing calc and uniform density, then its just slicing the thing up and calculating the moments about, say, the origin.

if the thing has varying density, then almost definitely calculus and triple integrals....