The addition formulae and trigonometric identities are used to simplify or evaluate trigonometric expressions. Trigonometric equations are solved using a double angle formulae and the wave function.

Think of trigonometric identities as mathematical shortcuts – they reveal hidden connections between different trigonometric functions and provide smart ways to simplify complex expressions.

There are some trigonometric identities which you must remember in order to simplify trigonometric expressions when required. When you are asked to prove something, ignore the right hand side of ...