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<=10≤x≤1 ?
1 Answer
Sep 16, 2014
The answer is
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=π∫10e2xdx
=pi (e^(2x))/2|_0^1=πe2x2∣∣∣10
=pi/2[e^2-e^0]=π2[e2−e0]
=pi/2[e^2-1]=π2[e2−1]