For trig equations you need to decide on a method for finding the additional values and practice it ... Apart from that they are just equations
For all of this work make sure you have learnt the trig values for 0,30,45,60,90,180
Also the 2 basic rules of sin^2 + cos^2=1 and tan = sin/cos
Once you have learnt (or even better understood) all of the above
Practice, practice, practice
Hold my beer everyone I'm going to do trig.
Good luck though, practice makes perfect, every trig question can be answered using the identities, as TenOfThem said. Don't forget you can derive the other two square identities by diving by either or . Also, the double angle formulae come in handy a lot.