Hey everyone,

I am given the integral:

Evaluate the integral of f(x,y,z) = z(x^2 +y^2 +z^2)^(-3/2) over the part of the ball x^2 +y^2 +z^2 less than or equal to 81 defined by z greater than or equal to 4.5.

This is the top of the sphere. I know that theta runs from zero to 2pi, but I am very confused about how to find the angle phi, which runs from the z axis to a point P, and the distance from the origin to the point P, which we call Ro.

I need to find what they run between to calculate my integral. Any help would be appreciated. Thanks.