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

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       acosh, acoshf, acoshl - inverse hyperbolic cosine functions
SYNOPSIS
       #include <math.h>
       double acosh(double x);
       float acoshf(float x);
       long double acoshl(long double x);

DESCRIPTION
       These functions shall compute the inverse hyperbolic  cosine  of  their
       argument x.
       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 inverse
       hyperbolic cosine of their argument.
       For finite values of x < 1, a domain error shall occur, and   either  a
       NaN  (if  supported),  or  an  implementation-defined  value  shall  be
       returned.
       If x is NaN, a NaN shall be returned.
       If x is +1, +0 shall be returned.
       If x is +Inf, +Inf shall be returned.
       If x is -Inf, a domain error shall occur, and either  a  NaN  (if  sup-
       ported), or an implementation-defined value shall be returned.
ERRORS
       These functions shall fail if:
       Domain Error
              The x argument is finite and less than +1.0,  or 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
       None.
APPLICATION USAGE
       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
       cosh(), feclearexcept(), fetestexcept(), 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 .

IEEE/The Open Group                  2003                            ACOSH(3P)