# Unit Circle

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More Lessons for Trigonometry
Math Worksheets
In some other lessons, we have covered the three common trigonometry functions

sine,

cosine and

tangent using the basic SOH-CAH-TOA definition.

In this lesson, we will extend the definition of the trigonometry functions by using the unit circle.

A **unit circle** is a circle of radius one unit with its center at the origin.

## Sine Function

As illustrated in the following diagram:

For a point (*x*, *y*) on the unit circle; sin θ = ⇒ sin θ =* y *

## Cosine Function

As illustrated in the following diagram:

For a point (*x*, *y*) on the unit circle; cos θ = ⇒ cos θ =* x*

## Tangent Function

As illustrated in the following diagram:

For a point (*x*, *y*) on the unit circle; tan θ =

## Videos

Unit Circle - Angles from 0° to 360°. Angles from 0 to 2π

Unit Circle - Points (x, y) along the unit circle

The following video shows how the unit circle can be used in the definitions of sine, cosine and tangent.

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