Trigonometry starts with a study of right triangles and the relationships between ratios of sides. From there, the unit circle can be discussed and trigonometric functions defined. The lessons below cover these different topics.

## The basics

## Right-triangle trigonometry

- Defining and Using the Trigonometric Functions with Right Triangles
- How to Memorize the Definitions of the Trig Functions

## Evaluating trig functions

## Identities

## Downloads

- Blank Table of the Common Angles (for practice)