Like Russian dolls, these problems have one trig function inside another, such as sin-1(cos60). This is a type of problem that every trig teacher loves, so I've given them their own video. They're not too bad if you break it down and work from the inside out. I'll also show you a trick to spot whether they'll just cancel each other out, like in Arcsin[sin(60)].
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)