# ACOS function

## Description

Arccosine function. ACOS(x) returns the arccosine of x. The arccosine function is the inverse function of the cosine function and calculates the angle for a given cosine. X must be in the [-1..1] range. The result is an angle expressed in radians. To convert from radians to degrees, use the DEGREES function.

The argument x can be a real number, a complex number, or a matrix. When it is a matrix, the function returns a matrix with the same dimensions and with the ACOS function applied to all elements.

## Examples

ACOS(0) equals 1.5707963 (=PI/2)

ACOS(1) equals 0

## Calculator

## Graph

## Relation with ASIN and ATAN functions

## Related functions

## External links

## Recommended book

## Trigonometry: A Complete Introduction

Hugh Neill

Buy from Amazon

This book covers all areas of trigonometry including the theory and equations of tangent, sine and cosine, using trigonometry in three dimensions and for angles for any magnitude, related to triangles. Everything you will need is here in this one book. Each chapter includes not only an explanation of the knowledge and skills you need, but also worked examples and test questions.