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.

Easy!

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 .

So .

Finally,

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!

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