/* derived from /netlib/fdlibm */ /* @(#)e_acosh.c 1.3 95/01/18 *//* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice  * is preserved. * ==================================================== * */ /* __ieee754_acosh(x) * Method : *	Based on  *		acosh(x) = log [ x + sqrt(x*x-1) ] *	we have *		acosh(x) := log(x)+ln2,	if x is large; else *		acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else *		acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1. * * Special cases: *	acosh(x) is NaN with signal if x<1. *	acosh(NaN) is NaN without signal. */ #include "fdlibm.h" static const double one	= 1.0,ln2	= 6.93147180559945286227e-01;  /* 0x3FE62E42, 0xFEFA39EF */ 	double __ieee754_acosh(double x){		double t;	int hx;	hx = __HI(x);	if(hx<0x3ff00000) {		/* x < 1 */	    return (x-x)/(x-x);	} else if(hx >=0x41b00000) {	/* x > 2**28 */	    if(hx >=0x7ff00000) {	/* x is inf of NaN */	        return x+x;	    } else 		return __ieee754_log(x)+ln2;	/* acosh(Huge)=log(2x) */	} else if(((hx-0x3ff00000)|__LO(x))==0) {	    return 0.0;			/* acosh(1) = 0 */	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */	    t=x*x;	    return __ieee754_log(2.0*x-one/(x+sqrt(t-one)));	} else {			/* 1<x<2 */	    t = x-one;	    return log1p(t+sqrt(2.0*t+t*t));	}}