Here is a Summary of Trigonometric Identities you need to memorise. Do not rely on them being in the Formulae Booklet as you need to recognise them within the context of problems you are looking to solve.

Here is a Trigonometric Identity & Equation Question with the mark scheme, together with a video solution:

Trigonometric ID & Eqn Example (6:23)

Trigonometric ID & Eqn Example Solution

Further Practice:

Trig Identities & Equations 2008-10 Questions