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## Homework Statement

Here is exactly what the problem says:

Let T be a solid of density one that lies below x^2+y^2+z^2=9 and above the XY-plane.

a) Use the triple integral to find its mass.

b) Find the centroid.

## Homework Equations

I believe that this should be an integral in spherical coordinates. I know the relevant equation is p^2sin(phi) dpd(phi)d(theta).

## The Attempt at a Solution

Obviously the first step is to set up the triple integral in spherical coordinates. I set x^2+y^2+z^2=9 and changed it to p^2=9. This left me with the limits of integration for p being from 0 to 3. I know that theta's integral is normally from 0 to 2(pie). I have no clue how to solve for the 'phi' limits and obviously I can't complete the problem until I do. Please advise as soon as possible what I should do. Thanks!