Double Integral with Polar Coordinates

Problem:

Use polar coordinates to find the volume of the given solid.

Enclosed by the hyperboloid

$\displaystyle -x^{2} - y^{2} + z^{2} = 1$ and the plane $\displaystyle z=2$

My attempt:

I think I'm tripping up on the radius portion of this problem. I tried to solve the function for z and set the two bounds equal to find their intersection and therefore the radius. I substituted *z* for two while finding the radius, which is something I probably should not do. Any help would be great. Attached is an image of my attempt.

http://mikederoche.com/temp/Untitled-12.jpg