/* Copyright (C) 1994, 1998 by Thomas Glen Smith.  All Rights Reserved. */
/* acosh APL2 V1.0.1 ***************************************************
* Inverse hyperbolic cosine for real numbers.                          *
***********************************************************************/
#define INCLUDES MATH
#include "includes.h"
double acosh(rite)
double rite;
{
	Sqrt; Log;
	extern int aplerr;

	if (rite < 1e0) {
		aplerr = 136; /* Argument m/b >= 1. */
		return(0);
	}
	return(log(rite+sqrt(rite*rite-1.0)));
}