I'll just throw the three questions out first:
Both of those I need the exact answer
That I need simplified.
(this is all supposed to be revision, by the way)
For the first two we were told to draw a triangle, and put the values there to make solving the problem geometrically simple, but I was never really taught the difference between cosine and arcsine (or any of the other ones, for that matter), so I'm not sure how to proceed
The last one I just don't know how to do.