## FANDOM

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Definition

The unit circle is a set of points satisfying the equation:
$x^2 + y^2 = 1$

The unit circle is a graph of a circle with radius equal to 1. It is important in mathematics as sine and cosine (and therefore all other trigonometric identities such as tangent) are defined as follows:
if $\theta$ is an the angle between a line from the origin to a point on the circle and the x-coordinate, $\sin(\theta) = y$ and $\cos(\theta) = x$.