NAME
acosh() — inverse hyperbolic cosine function
SYNOPSIS
#include <math.h>
double acosh(double x);
DESCRIPTION
The
acosh()
function computes the inverse hyperbolic cosine of its argument.
The ISO/ANSI C committee has approved the
acosh()
function for inclusion in the C9X draft standard.
To use this function, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options. Make sure your program includes
<math.h>.
Link in the math library by specifying
-lm
on the compiler or linker command line.
RETURN VALUE
The
acosh()
function returns a value in the range +zero to +INFINITY.
If
x
is
+INFINITY,
acosh()
returns
+INFINITY.
If
x
is NaN,
acosh()
returns NaN.
If
x
< 1.0,
acosh()
returns NaN and sets
errno
to [EDOM].
ERRORS
If
acosh()
fails,
errno
is set to the following value.
- [EDOM]
x
is less than 1.0.
STANDARDS CONFORMANCE
acosh(): SVID3, XPG4.2
