00:01
For this problem, we need to show that this integral is equal to negative 1 raised to n times 4 pi over n squared.
00:08
To do this, we need to apply integration by parts.
00:11
We let u be x squared and dv is cosine of nx dx.
00:20
And so du is just 2x dx dx while v is sine of nx over n.
00:28
So by integration by parts, we have the integral from negative pi to pi of x squared cosine of nx d x.
00:40
This is just uv minus v -d -u, that's x squared times sine of nx over n minus the integral of sine of nx over n times 2x d x.
00:59
So simplifying this, we get x squared sine of nx over n, minus we have 2 over n, integral of sine x, sign of nx dx.
01:14
Now from here we want to apply integration by parts again.
01:17
We let u bx and dv be sine of nx d x d x...