## The unit circle definition of sine, cosine, & tangent

## Unit Circle:

**A unit circle intends a circle with a radius of 1 unit.**

It is an excellent idea to understand and communicate regarding lengths and trigonometric functions.

In the fig. where the x-axis and y-axis cross, so we can calculate the neat arrangement here.

## Sine, Cosine and Tangent

### The trig functions & right triangle trig ratios

As we know the radius of the circle is 1, then we can immediately calculate sine, cosine, and tangent.

**What happens when we put the angle, θ, is 0°?**

cos 0° = 1,

sin 0° = 0

and tan 0° = 0

**What happens when we put the angle, θ, is 90°?**

cos 90° = 0,

sin 90° = 1

and tan 90° = undefined