Originally Posted by

**pakman** The problem states to find the mass of a solid inside a sphere of radius 2a and outside a circular cylinder of radius a whose axis is a diameter of the sphere, if the density is proportional to the square of the distance from the center of the sphere.

So I'm imagining a sphere, let's say centered around xyz = 0. Then a cylinder comes into play, which it seems to me like it has the same radius as the sphere. However, I'm not sure what it means by saying "whose axis is a diameter of the sphere."