00:01
Yes, so the surface area of a solid of revolution around the x -axis is equal to 2 pi times the integral going from a to b of the function f of x times the square root of 1 plus the derivative f prime of x squared the x.
00:25
So here we're given that f of x is well equal to 2 minus x, and therefore the derivative f prime of x is just equal to negative 1.
00:37
Our interval is from 0 to 2.
00:39
So to calculate this, we can factor out the constant, which is going to be 2 pi times the square root of 2, and then times the integral going from 0 to 2 of just 2 minus x d x.
00:54
Well, that's going to be equal to 2 pi times the square root of 2, and then times 2x minus x squared over 2, evaluated from 0 to 2.
01:07
So evaluating, we just get 4 minus 2, which is 2, and then the surface area is just going to be 2 pi square root of 2 times 2, which is equal to 4 pi times the square root of 2, which is equal to 4 pi times the square root of 2...