# Trig unit circle review

Review the unit circle definition of the trigonometric functions.

## What is the unit circle definition of the trigonometric functions?

The unit circle definition allows us to extend the domain of sine and cosine to

**all real numbers**. The process for determining the sine/cosine of any angle is as follows:- Starting from , move along the unit circle until the angle that is formed between your position, the origin, and the positive -axis is equal to .
- is equal to the -coordinate of your point, and is equal to the -coordinate.

The other trigonometric functions can be evaluated using their relation with sine and cosine.

*Want to learn more about the unit circle definition? Check out this video.*

## Appendix: All trig ratios in the unit circle

Use the movable point to see how the lengths of the ratios change according to the angle.