COS(3P)                                             POSIX Programmer's Manual                                            COS(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       cos, cosf, cosl - cosine function

SYNOPSIS
       #include <math.h>

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


DESCRIPTION
       These functions shall compute the cosine of their argument x, measured in radians.

       An  application  wishing  to  check  for  error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)
       before calling these functions.  On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO |  FE_OVERFLOW
       | FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE
       Upon successful completion, these functions shall return the cosine of x.

       If x is NaN, a NaN shall be returned.

       If x is +-0, the value 1.0 shall be returned.

       If  x  is +-Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be
       returned.

ERRORS
       These functions shall fail if:

       Domain Error
              The x argument is +-Inf.

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


       The following sections are informative.

EXAMPLES
   Taking the Cosine of a 45-Degree Angle
              #include <math.h>
              ...
              double radians = 45 * M_PI / 180;
              double result;
              ...
              result = cos(radians);

APPLICATION USAGE
       These functions may lose accuracy when their argument is near an odd multiple of pi/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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

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

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open  Group
       Standard   is   the   referee   document.   The   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                       COS(3P)