# cos (3)

# NAME

cos, cosf, cosl - cosine function# SYNOPSIS

#include <math.h>

Link withdouble cos(doublex);float cosf(floatx);long double cosl(long doublex);

*-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

|| /* 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).

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)