Volume of a solid of revolution (shell method)

The region bounded by the graphs of two functions is rotated around y-axis. You can eneter your own functions (g(x) must be less than f(x) for all x in the interval [a,b] !). A typical cylindrical shell (in green) is also shown and can be animated. The animation demonstrates how the volume of the solid is approximated by the sum of volumes of cylindrical shells.