Tangent
 A line that meets a smooth curve at a single point and does not cut across the curve.
 Or
 A trigonometric function. The trigonometric function of angle A is defined as:

 Note: In this series A is in radians and
 The following expression is also known as the half angle formula:
See also: Cosecant, Cosine, Cotangent, Secant, Series Expansions, Sine, Tangential, Trigonometric Functions.
Subjects: Trigonometry