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cos - Man Page

cosine function


Math library (libm, -lm)


#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


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.


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).

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


C11, POSIX.1-2008.


C89, POSIX.1-2001.

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


Before glibc 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)

Referenced By

acos(3), asin(3), atan(3), atan2(3), dlopen(3), sin(3), sincos(3), tan(3), unu-1op(1).

The man pages cosf(3) and cosl(3) are aliases of cos(3).

2024-05-02 Linux man-pages 6.9.1