# Volumes using integration

1. Mar 22, 2013

### EngnrMatt

1. The problem statement, all variables and given/known data

Find the volume of the solid formed by revolving the functions: y=x2 and y=1 about the line y=6

2. Relevant equations

∏∫(ro2-ri2)dx

3. The attempt at a solution

I found the outer radius to be (1-x2)-6 and my inner radius to be -6. Also, the limits of integration were -1 and 1. Plugging it all in got -224/15. This is obviously wrong because it is negative, and the positive value didn't work either. Does anyone have a clue on how to do this?

2. Mar 22, 2013

### Dick

Isn't the inner radius the distance from y=1 to y=6? Isn't that 5? What's the outer radius?

3. Mar 23, 2013

### EngnrMatt

Yes, you are right. I see now, the outer radius will be the distance between y=6 and the lower function and the inner will be the distance between y-6 and the upper function. It worked by the way, thanks.