Volume of Solid: Frustum of Right Circular Cone

[fk378]

Homework Statement

Find the volume of the solid S.

A frustum of a right circular cone with height h, lower base radius R, and top radius r.

Homework Equations

the integral of (pi)(r^2) [top] - (pi)(r^2) [bottom] dx

The Attempt at a Solution

I don't know how to start. I know I need to find the endpoints where the cross sections meet, but I'm not sure how to go about that.

 

[e(ho0n3]

Divide the frustrum into circles of thickness dy. The area of the circle will be a function of y. Integrate to find the volume.