User:Llightex/Cosine

The cosine (abbreviated cos) is a trigonometric function of an angle, which is defined in a triangle as the ratio of the length of the adjacent side to the length of the hypotenuse. In our case


 * $$\cos A = \frac {\textrm{adjacent}} {\textrm{hypotenuse}} = \frac {b} {h}.$$

Identities
The reciprocal of cosine is defined as the secant function. (Similarly, the reciprocal of sine is cosecant)

The inverse of the cosine function is known as the arccosine, represented $$arccos(x)$$ or $$cos^{-1}(x)$$.