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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 dif-
       fer (consult 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 feclearex-
       cept(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 excep-
       tion 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  indepen-
       dent 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, Section 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (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 Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                              COS(3P)