I'm having a bit of trouble solving this trig problem:

At first when I looked at it it seemed easy but as I tried to solve it, it got really confusing and I got stuck on the part.Find the General solution for...

Here's what I did:

Double angle formula:

Double angle formula:

Now I can get the general solution for the part but what about the part? How would I solve that?

EDIT: Sorry I just realised I placed this in the wrong section :/

Can a mod please move it to the trig section?