# 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**():

_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

## DESCRIPTION

The
**cos**() function returns 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. 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

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