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,  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  Operating  System
       Interface  (POSIX), The Open Group Base Specifications 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
       Standard, 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 .