# COS function

## Description

Cosine function. COS(x) returns the cosine of an angle x. The result range is [-1..1]. The argument x must be expressed in radians. To convert degrees to radians you use the RADIANS function.

*Sine and Cosine in unit circle*

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 COS function applied to all elements.

## Examples

COS(PI()/3) equals 0.5.

COS(RADIANS(90)) equals 0.

COS(3.14159265) equals -1.

## Calculator

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## 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.