Unit Circle Trigonometry

The unit circle demonstrates the output of the trigonometric functions sine, cosine and tangent.

Description

This figure illustrates the geometry of the trigonometric functions on the unit circle. Note, although the figure is cropped to show the right quadrant of the unit circle, the lengths of the inscribed right-triangle correspond to the output of the trigonometric functions for any point along the unit circle.

Geometry Function
Geometry of the Sine Function Sine Function
The output of sine corresponds to the distance from a point on the perimeter of the unit circle to the -axis.
Geometry of the Cosine Function Cosine Function
The output of cosine corresponds to the distance from a point on the perimeter of the unit circle to the -axis.
Geometry of the Tangent Function Tangent Function
The output of tangent corresponds to the length of the line tangent to a point on the unit circle starting from the point and intersecting with the x-axis.
Geometry of the Cotangent Function Cotangent Function
The output of cotangent corresponds to the length of the line tangent to a point on the unit circle starting from the point and intersecting with the y-axis.

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