cos, cosf, cosl - cosine function

```
#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)):

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

These functions return the cosine of `x`

, where `x`

is given in radians.

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.

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.

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

Interface | Attribute | Value |

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

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

The variant returning `double`

also conforms to SVr4, 4.3BSD.

Before version 2.10, the glibc implementation did not set `errno`

to **EDOM** when a domain error occurred.

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

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/.