# Thread: Help with integration using disks or shells

1. ## Help with integration using disks or shells

I need help with this problem:

Consider the region R, bounded by y=-4cos(x) and y=2.

I can use either disks or shells to solve this problem.

I need help setting up the integral required to find the volume of the solid obtained by revolving the region R about the line y=1.

I think to set up this integral you would use this integral:

2PI∫from 2 to 4 (x-1)(-4cos(x)) using

shells.

I'm not sure if I've set this integral up right.Have I done something wrong? Thanks in advance to all who can help,

2. $y = -4\cos{x}$ and $y = 2$ intersect at many places, forming many regions.

$-4\cos{x} = 2$

$\cos{x} = -\frac{1}{2}$

$x = 2k\pi \pm \frac{2\pi}{3} \, , \, k \in \mathbb{Z}$

which region are you looking at to rotate, specifically?