---
title: Unit Circle
---
## Unit Circle

A unit circle is a circle with an r (radius) of value 1. It is frequently used, centered at coordinates 0,0, in the cartesian coordinate system as a part of trigonometry.

The interior of a unit circle, not including the outer circle,  is called the open unit disk, when the circle itself is also included it is referred to as the closed unit disk.

### More Informaction
https://en.wikipedia.org/wiki/Unit_circle

