## anonymous 5 years ago Help me integrate $\int\limits_{}^{} \sin^5 3x \cos ^3 3x dx$

1. watchmath

Use $$u=\sin (3x)$$. Then $$du=3\cos(3x)\,dx$$ The integral become $$\frac{1}{3}\int u^5\cos^2(3x)\,du=(1/3)\int u^5(1-u^2)\, du$$

2. anonymous

Wow thank you!