As promised, we will look at this time. It might get boring, as the method is exactly the same as as they are quite related.
This requires double angle formula:
Here we introduce trigo identity:
Here we have a problem!
But recall we did some really similar in part 1, and notice that is the derivative () of .
Here we can apply double angle a few times to break it down before integrating.
After seeing both part 1 and part 2, you should notice some intuitive method.
Consider and .
Should n be even, we introduce the double angle formula to simplify things.
Should n be odd, we introduce the trigonometry identities and integrate. We must apply method to integrate. Just saying, .
Tell me what you think in the comments section!