cos(P)                                                   cos(P)





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
       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 argu-
       ment 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 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 /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, 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,
       Standard  for Information Technology -- Portable Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute 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 .



POSIX                         2003                       cos(P)
