The cotangent of an angle is the reciprocal of the tangent of an angle. On the unit circle, the cotangent of an angle is equal to the adjacent side of a right triangle with an opposite side of length . Geometrically, the cotangent corresponds to the length of the line tangent to the point formed by the angle on the unit circle that intersects with the y-axis.

The graph of cotangent and tangent shows the reciprocal relationship between the two functions. As tangent approaches so does cotangent and as tangent approaches cotangent diverges to infinity.

See the rest of the trigonometric identities below:

Trigonometric identities are a set of equations derived from the properties of triangles and circles. The identities are used to transform and manipulate math expressions.