# Math Help - Integration query

1. ## Integration query

Integral of cos(^3)2x
i did - cos2x X cos(^2)2x
Then changed cos(^2)2x to 1-sin(^2)2x
How do i proceed now?

2. The derivative of $\sin^2(2x)$ is $4\sin(2x)\cos(2x)$.

3. Yes ok, i substituted that.what do i do next?

4. I would probably do a $u$ substitution from your $\cos(2x)(1-\sin^{2}(2x)):$ $u=\sin(2x).$

5. Yes,the substitution worked.Thanks
But is there also any other way to do it?

6. Yes.

$\cos3{\theta} = 4\cos^3{\theta} - 3\cos{\theta}$

From the above equation find cos^3(x) and then find the integration.