How do you find the surface area of the solid obtained by rotating about the xx-axis the region bounded by y=e^xy=ex on the interval 0<=x<=10x1 ?

1 Answer
Sep 16, 2014

The answer is pi/2[e^2-1]π2[e21].

Since you are only given a single function and we are rotating about the axis of the parameter, this requires the disk method. The disk method is:

V=int_a^b AdxV=baAdx
=int_a^b pi r^2dx=baπr2dx
=int_a^b pi [f(x)]^2dx=baπ[f(x)]2dx

We have the known values:

f(x)=e^xf(x)=ex
a=0a=0
b=1b=1

And now we can substitute:

V=int_0^1 pi (e^x)^2dxV=10π(ex)2dx
=pi int_0^1 e^(2x)dx=π10e2xdx
=pi (e^(2x))/2|_0^1=πe2x210
=pi/2[e^2-e^0]=π2[e2e0]
=pi/2[e^2-1]=π2[e21]