00:01
Okay, so the problem is to integrate x squared ds doing the line integral on the curb c, but it's only from 4 -0 to 04.
00:14
And if you sketch this out, this is one four of a circle, radius and 4 right here.
00:21
So this portion is going counterclockwise.
00:24
So the easiest way is to turn this into polar coordinate, so that's actually integral.
00:30
It's going to be 1 -4 of the integral.
00:33
Actually, you don't need the 1 -4.
00:36
It's going to be integral from 0 to pi over 2 because that's how much your angle move is 0 to pi over 2.
00:44
Let's see 0, pi over 2.
00:46
And x square, and you know the x is, what is x? x is r cosy theta.
00:53
In this case, r is 4, so it's going to 4 cosy theta.
00:56
So x squared, so it's going to be 16, cosine square, theta, d -teta...