cos(3)

cos3

Cosine function

Usage

#include <math.h>

double cos(double x); float cosf(float x); long double cosl(long double x);

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

Library

Math library (libm, -lm)

Overview

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).

InterfaceAttributeValue
cos(), cosf(), cosl()Thread safetyMT-Safe

Releases

19 releases since Debian 1.1 (Buzz); the text changed 13 times.

  1. 1.1–2.2
  2. 3.0
  3. 3.1
  4. 4.0
  5. 5.0
  6. 6.0
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. Arch

Standards

C11, POSIX.1-2008.

History

C89, POSIX.1-2001.

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

Bugs

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

From man-pages 6.19-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.