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. 

To use this function, link in the math library by specifying −lm on the compiler or linker command line. 

RETURN VALUE

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. 

SEE ALSO

cosh(3M), asinh(3M), atanh(3M), isinf(3M), isnan(3M). 

STANDARDS CONFORMANCE

acosh(): SVID3, XPG4.2

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996