# Triple integral, I need a little help

1. Nov 3, 2004

I have a group of problems that deals with the equations:

f(x,y)= x^2+y^2
g(x,y)=20-(x-4)^2-(y+2)^2.

I know that the surfaces z=f(x,y) and z=g(x,y) intersect in a closed curve, C, and the projection of C onto the xy-plane is a circle. However, I am having trouble finding its xy-equation, center, and radius. Additionally and more importantly, I am in the dark on setting up the double or triple integral for the volume of the region bounded by z=f(x,y) and z=g(x,y). Can anyone please help.

2. Nov 3, 2004

### Tide

The two surfaces intersect along a circle centered at (x, y) = (2, -1) with a radius of $\sqrt 5$ so you might consider a coordinate transformation placing (2, -1) at the new origin.