# COS

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

BUGS

SEE ALSO

COLOPHON

## NAME

cos, cosf, cosl
- cosine function

## SYNOPSIS

**#include
<math.h>**

**double
cos(double** *x***); **

float cosf(float *x***); **

long double cosl(long double *x***);**

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 versions <= 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).

## 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 4.15 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/.