Triganometric identities

A few of them anyway

The Pythagorean triganometric identity

In this right triangle …

Right triangle

Pythagoras’ Theorem states that . Dividing both sides by then gives us . Since the definitions of and are, respectively, and , the above identity follows immediately.

Simple manipulation gives us the following additional identities …

Angle sum and difference identities

Double angle sum identities

These follow immediately from the angle sum identities.