Trig

How are people remembering trig identities I can't get them to stick any methods?

By practicing enough questions where you apply them.

My advice in maths, the only things you should remember are definitions... even then, you need to be able to apply them which takes practice.

Take it from someone who got 100 in C3 without any natural ability for maths, which is very trig heavy, when you get enough practice you'll be fine and you'll have trig identities coming out your ears... I call them cottan buds.

How are people remembering trig identities I can't get them to stick any methods?

Just remember that $\sin^2(x)+\cos^2(x) \equiv 1$
and then $\tan^2(x)+1 \equiv \sec^2(x)$ and $1+\cot^2(x) \equiv \csc^2(x)$ fall out naturally - first is division by $\cos^2(x)$ and the second is divison by $\sin^2(x)$

Of course, $\frac{\sin(x)}{\cos(x)} \equiv \tan(x)$ is the other you have to remember.

Compound angle formulae are in the booklet.