# Trigonometric identities

A mathematical identity that expresses a mathematical relation between trigonometric functions is called a trigonometric identity.

## Basic identities

There are four types of fundamental trigonometric identities in trigonometry. If you are a beginner, start your learning from the following four trigonometric rules.

1. Quotient identities
2. Pythagorean identities
3. Reciprocal identities
4. Product identities