00:01
So we're going to, we're being asked to find the surface area of revolution for y is equal to x cubed over the interval 0 to 2.
00:15
So let's put down the equation for the surface area here.
00:19
So 2 pi, s is 2 pi into integral of a to b of f of x, which is y here.
00:27
So f of x is y is x cubed, multiplied by 1 plus f prime of x squared d x.
00:40
All right, so we know that f of x is x cubed.
00:45
F of x is equal to x cubed.
00:48
And f prime of x now will be 3x squared.
00:53
Okay, so let's plug those values into our equation.
00:55
So s is 2 pi, a to b, which is 0, 2, into x cubed times 1 plus 3x squared squared.
01:13
So that's also the integral of 2 pi, integral of 0 .5.
01:17
0 to 2 of x cubed into square root of 1 plus 9 x to the 4.
01:23
Well, the way to integrate this is using something called substitution.
01:29
So here's what i'm going to do...