Question

Help me integrate
\[\int\limits_{}^{} \sin^5 3x \cos ^3 3x dx\]

Answer 1

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

Answer 2

Wow thank you!