I'm having a lot of problems with this topic. I know what the sine, cosine and tan graphs look like.

one question i come across fequently is "given that sin 30°, what is a) sin 150° b) sin 330°. - i can work it out on a calculator but the questions on a non-calc paper. Im presuming it's something about the graph having repetitions above and below the x axis.

another question tat frequently pops up is something like "find two different values of x between 0 and 180 for which sin (2x)° = sin 30°". I can work out one of them as 15° but cannot find the second solution and would like to know how it can be found.