Lecture 24 : Volume of solids of revolution by washer method [Section 24.1]
We describe next the slice method, as discussed in the previous section, as applied to solids of revolution.
24.1.3
Washer Method:
Let be the plane region between the two curves given by the functions
which are Riemann integrable and
Then, for the solid obtained by revolving about the , the slice of thickness at is a circular washer of inner radius and of outer radius . Thus, its cross sectional area is .
Therefore, the volume of the corresponding solid of revolution is given by
be the plane region between the two curves given by the functions 
about the 
, the slice of thickness 
at 
is a circular washer of inner radius 
and of outer radius 
. Thus, its cross sectional area is 
. 
