IEEE Std 1003.1-2001

Copyright © 2001 The IEEE and The Open Group, All Rights reserved.

cos, cosf, cosl - cosine function

#include <math.h>

double cos(doublex);

float cosf(floatx);

long double cosl(long doublex);

^{[CX]}The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.These functions shall compute the cosine of their argument

x, measured in radians.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Upon successful completion, these functions shall return the cosine of

x.

^{[MX]}Ifxis NaN, a NaN shall be returned.If

xis ±0, the value 1.0 shall be returned.If

xis ±Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.

These functions shall fail if:

- Domain Error
^{[MX]}Thexargument is ±Inf.If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

errnoshall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

## Taking the Cosine of a 45-Degree Angle

#include <math.h> ... double radians = 45 * M_PI / 180; double result; ... result = cos(radians);

These functions may lose accuracy when their argument is near an odd multiple of /2 or is far from 0.

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

None.

None.

acos() ,feclearexcept() ,fetestexcept() ,isnan() ,sin() ,tan() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

The

cosf() andcosl() functions are added for alignment with the ISO/IEC 9899:1999 standard.The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.

IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.

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