/* acosh.c - ANSI math routines *//* Copyright 1992 Wind River Systems, Inc. *//*modification history--------------------01d,14oct92,jdi  made acosh() nomanual.01c,13oct92,jdi  mangen fixes01b,20sep92,smb  documentation additions01a,08jul92,smb  documentation*//*DESCRIPTION* Copyright (c) 1985 Regents of the University of California.* All rights reserved.** Redistribution and use in source and binary forms are permitted* provided that the above copyright notice and this paragraph are* duplicated in all such forms and that any documentation,* advertising materials, and other materials related to such* distribution and use acknowledge that the software was developed* by the University of California, Berkeley.  The name of the* University may not be used to endorse or promote products derived* from this software without specific prior written permission.* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.** All recipients should regard themselves as participants in an ongoing* research project and hence should feel obligated to report their* experiences (good or bad) with these elementary function codes, using* the sendbug(8) program, to the authors.*SEE ALSO: American National Standard X3.159-1989NOMANUAL*/#include "vxWorks.h"#include "math.h"#if defined(vax)||defined(tahoe)	/* VAX D format */#ifdef vax#define _0x(A,B)	0x/**/A/**/B#else	/* vax */#define _0x(A,B)	0x/**/B/**/A#endif	/* vax *//* static double *//* ln2hi  =  6.9314718055829871446E-1    , Hex  2^  0   *  .B17217F7D00000 *//* ln2lo  =  1.6465949582897081279E-12   ; Hex  2^-39   *  .E7BCD5E4F1D9CC */static long     ln2hix[] = { _0x(7217,4031), _0x(0000,f7d0)};static long     ln2lox[] = { _0x(bcd5,2ce7), _0x(d9cc,e4f1)};#define    ln2hi    (*(double*)ln2hix)#define    ln2lo    (*(double*)ln2lox)#else	/* defined(vax)||defined(tahoe) */static doubleln2hi  =  6.9314718036912381649E-1    , /*Hex  2^ -1   *  1.62E42FEE00000 */ln2lo  =  1.9082149292705877000E-10   ; /*Hex  2^-33   *  1.A39EF35793C76 */#endif	/* defined(vax)||defined(tahoe) *//******************************************************************************* acosh - compute the inverse hyperbolic cosine of <x>** This routine returns the inverse hyperbolic cosine of <x>* in double precision (VAX D Format 56 BITS, IEEE Double 53 BITS).** Required system support function: sqrt()** Required kernel function:* .CS*	log1p(x) 		...return log(1+x)* .CE** Based on acosh(x) = log [ x + sqrt(x*x-1) ] we have* .CS*     acosh(x) := log1p(x)+ln2,	if (x > 1.0E20); else*     acosh(x) := log1p( sqrt(x-1) * (sqrt(x-1) + sqrt(x+1)) ) .* .CE* These formulae avoid the over/underflow complication.** Special cases are acosh(x) is NaN with signal if x<1 and acosh(NaN) * is NaN without signal.** RETURNS: The inverse hyperbolic cosine of <x>.* It returns the exact inverse hyperbolic cosine of <x> nearly* rounded. In a test run with 512,000 random arguments on a VAX, the* maximum observed error was 3.30 ulps (units of the last place) at* x=1.0070493753568216.** INTERNAL* Coded IN C BY K.C. NG, 2/16/85;* Revised BY K.C. NG on 3/6/85, 3/24/85, 4/16/85, 8/17/85.** NOMANUAL*/double acosh(x)double x;{	double log1p(),sqrt(),t,big=1.E20; /* big+1==big */#if !defined(vax)&&!defined(tahoe)	if(x!=x) return(x);	/* x is NaN */#endif	/* !defined(vax)&&!defined(tahoe) */    /* return log1p(x) + log(2) if x is large */	if(x>big) {t=log1p(x)+ln2lo; return(t+ln2hi);}	t=sqrt(x-1.0);	return(log1p(t*(t+sqrt(x+1.0))));}