Chapter 6.3, Problem 31E

Disk method Let R be the region bounded by the following curves. Use the disk method to find the volume of the solid generated when R is revolved about the x-axis.

21. y = sin x on [0, π], y = 0 (Recall that ${\sin }^{2}x=\frac{1}{2}(1-\cos 2x)$.)