Thread: Trig Equality

When doing some trig practice in my free time, I came across the problem if , find .

I did a little research online, and I found that , which simplified the problem greatly, and I was able to find that the answer is . Nevertheless, I feel that there is probably a "cleaner" way of doing this that does not require knowing the above equivalence.

Does anyone have any suggestions on how to attempt this question? Thanks!

Use following facts :

Thank you very much! That made it so easy to do!