1. Area Between Two Curves
Math 5A

2. The Problem
Find the volume of the solid formed when the region bounded by y=sqrt(x) , x=4 and the x axis is revolved about the x axis.

3. The Idea Behind the Solution
Suppose we tried slicing this solid into 4 pieces by slicing perpendicular to the x axis.
Those four slices would look approximately like the four circular disks shown at the right, only the outer surface would not be as straight. We can approximate the volume of the solid by computing the volume of these four disks.

4. Finding the Volume of the Disks
The volume of each disk is pr2h where h is the thickness of each disk
(1 in this case, in general) and r is the functional value at a a point in the subinterval.

5. Volume for 4 disks
Approximation using 4 disks. For a better approximation, use more disks.

6. 16 Disks.

7. 64 Disks

8. 1024 Disks – Approx. Volume 25.16

9. The Disk Method – Just add up the
For a solid formed by revolving a region bounded above by f(x) on [a,b] about the x axis…