1. reduction formula

Hey All,

sorry for the over flow of questions today. got exam very soon..

I need some help in the following question :

thanks

2. what I don't get is how would I apply the integration by parts to cos^nxdx ??

what is u and dv?

3. Differenciate both sides.

And use the fact that the derivative of I_n is cos^n x

4. how would I differentiate both sides

5. I don’t think that differentiation is the way to proceed with it.
Here is as pdf file that I wrote with EXP and Acrobat distiller.
I used parts.