# Math Help - Spherical coordinates

1. ## Spherical coordinates

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."

2. 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."
The right circular cylinder is embedded inside the sphere. What they are saying is that the axis of symmetry of the cylinder is along one of the diameters of the sphere. That is to say, the cylinder is "centered" inside the sphere, not off-centered, if that helps.

-Dan