I am trying to find the volume of a quarter circle that is rotated about . So the equation should look like this:

This should simplify to:

If I am doing this right thus far, then the integral is:

from 0 to

And when I plug these values in I some how end up with

I feel like I am missing something in between here, or maybe just made an error plugging in the values, although I have tried it a few times and end up with the same answer. Is this right? Thanks for the help.