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**NAME**

cos, cosf, cosl - cosine function

**SYNOPSIS**

#include<math.h>doublecos(doublex);floatcosf(floatx);longdoublecosl(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):cosf(),cosl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; orcc-std=c99

**DESCRIPTION**

Thecos() function returns the cosine ofx, wherexis given in radians.

**RETURN** **VALUE**

On success, these functions return the cosine ofx. Ifxis a NaN, a NaN is returned. Ifxis positive infinity or negative infinity, a domain error occurs, and a NaN is returned.

**ERRORS**

Seemath_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Domain error:xis an infinityerrnois set toEDOM(but see BUGS). An invalid floating-point exception (FE_INVALID) is raised.

**CONFORMING** **TO**

C99, POSIX.1-2001. The variant returningdoublealso conforms to SVr4, 4.3BSD.

**BUGS**

Before version 2.10, the glibc implementation did not seterrnotoEDOMwhen a domain error occurred.

**SEE** **ALSO**

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

**COLOPHON**

This page is part of release 3.35 of the Linuxman-pagesproject. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man- pages/. 2010-09-11 COS(3)