# cos - Man Page

cosine function

## Synopsis

#include <math.h> double cos(doublex); float cosf(floatx); long double cosl(long doublex);

`Link with `

*-lm*.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

**cosf**(), **cosl**():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

## Description

These functions return the cosine of *x*, where *x* is given in radians.

## Return Value

On success, these functions return the cosine of *x*.

If *x* is a NaN, a NaN is returned.

If *x* is positive infinity or negative infinity, a domain error occurs, and a NaN is returned.

## Errors

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

- Domain error:
*x*is an infinity *errno*is set to**EDOM**(but see Bugs). An invalid floating-point exception (**FE_INVALID**) is raised.

## Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |
---|---|---|

cos(), cosf(), cosl() | Thread safety | MT-Safe |

## Conforming to

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning *double* also conforms to SVr4, 4.3BSD.

## Bugs

Before version 2.10, the glibc implementation did not set *errno* to **EDOM** when a domain error occurred.

## See Also

acos(3), asin(3), atan(3), atan2(3), ccos(3), sin(3), sincos(3), tan(3)

## Colophon

This page is part of release 5.13 of the Linux *man-pages* project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

## Referenced By

acos(3), asin(3), atan(3), atan2(3), dlopen(3), sin(3), sincos(3), tan(3).

The man pages cosf(3) and cosl(3) are aliases of cos(3).