HP-UX Reference (11i v1 05/09) - 3 Library Functions A-M (vol 6)

acosh(3M) acosh(3M)

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.