If the equation contains trig functions with the same angle and some of them are squared then it may be possible to use a Pythagorean identity to write an equation in the same trig. function which may then possibly factorise.

In these examples I show you how the Pythagorean identities help solve some equations.

Pythagorean Identities:

- sin
^{2}θ + cos^{2}θ ≡ 1 - 1 + tan
^{2}θ ≡ sec^{2}θ - 1 + cot
^{2}θ ≡ cosec^{2}θ