1.5: Surface Area of Revolution
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The area of a frustum is
A=2πr(length).
If we revolve a curve around the x-axis, we have that the surface area of revolution is given by
Area=2π∫bay√1+(dydx)2dx.
Set up an integral that gives the surface area of revolution about the x axis of the curve
y=x2
from 2 to 3.
Solution
We find
(dydx)2=(2x)2=4x2.
Now use the area formula:
A=2π∫32x2√1+4x2dx.
We will learn later how to work out this integral. However a computer gives that
A≈208.09.
Larry Green (Lake Tahoe Community College)
Integrated by Justin Marshall.