thanks! helped a lot. Im not sure i always get to a certain point and just get stuck

You are most welcome!
Please forgive my impertinence as I hazard to suggest to you three pointers to trigo proof-questions.

Firstly, start the proof from the more complicated side.

Secondly, express all trigo identities in terms of sine and cosine.

Thirdly, keep an eye on the other side you are attempting to arrive at by gearing towards the form shown on the other side.

I hope this helps. Regards