I'm having a difficult time with this problem and can't seem to make much progress:

Let be a catenary. Find the volume of the solid obtained by revolving the region under the graph of the catenary on the interval [-b,b], (b>0) about the x-axis.

So, I have decided that based on definitions of hyperbolic functions. The problem I am having is setting up a formula to figure out the area. By using shell or disk method I can't get an exact area, only a formula since there isn't a specific interval.