# Unit Circle Trigonometry

This figure illustrates the trigonometry of the unit circle that corresponds to the circle definitions of the trigonometric functions. The circle definitions of sine and cosine are shown below:

Substituting into the definitions we can see the relationship between the functions and the point on the unit circle defined by the angle (theta). The coordinate of the point is equal to the sine of the angle and the coordinate of the point is equal to the cosine of the angle.

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There are six trigonometric functions that relate to the geometry of the right-triangle sine, cosine, tangent, cosecant, secant, and cotangent. The functions take the angle of a right triangle as input and return a ratio of two of its sides.

The sine function returns the sine of a number provided in radians. In geometric terms, the function returns the vertical component of the point formed by the angle on the unit circle.

The cosine function returns the cosine of an angle provided in radians. In geometric terms, the function returns the ratio of the right-triangle's adjacent side over its hypotenuse.