# Axis of revolution-washer/disks

1. Jul 5, 2013

### emk

Y=x^2, y=0, x=1 ; about x=2

v=pi r^2 T

I tried 0 to 1 intg (x^3-2)^2+2^2 dx, but it wasn't right. Not sure what to do.

2. Jul 5, 2013

### SteamKing

Staff Emeritus
We're not sure what you are doing, either.

Use the homework template and give a complete problem statement.

3. Jul 5, 2013

### QuarkCharmer

It may help to break that thing up into two different integrals. The thing is shaped like a circus tent. That is, a cylinder with a spire on top. The cylinder integration can be done without calculus. Then do the spire part using your books formula (the formula for volume basically) and add the two.

4. Jul 5, 2013

### verty

I see no spire on top, just an oddly-shaped cylinder.

5. Jul 5, 2013

### haruspex

QuarkCharmer's description makes sense to me. The point of the spire is at x=2, the axis of revolution. But the washer method just seems to complicate matters. emk, were you told to use that method here?

6. Jul 5, 2013

### emk

Yes, either the disk or washer method.

7. Jul 5, 2013

### QuarkCharmer

Unless I am mistaken:

You could easily find all these intersection points, and rewrite the equation to integrate such that the integration makes more sense to you.