Thread: [SOLVED] Finding volume with integration

f(x)=4sinx on (0, pi)
Find the volume of a 3d-solid obtained by rotating this region about the dashed line y=-1

I realize this is just like a regular integration volume equation but I'm having trouble distinguishing the radii.

V= pi (0---pi) (R^2-r^2) dx

Is r=4 and then R=(f(x)-f(-1))? And how would I write this in the above formula so as to be able to integrate it?

Thanks in advance!

Originally Posted by yzobel

f(x)=4sinx on (0, pi)
Find the volume of a 3d-solid obtained by rotating this region about the dashed line y=-1

I realize this is just like a regular integration volume equation but I'm having trouble distinguishing the radii.

V= pi (0---pi) (R^2-r^2) dx

Is r=4 and then R=(f(x)-f(-1))? And how would I write this in the above formula so as to be able to integrate it?

Thanks in advance!