0N/A
0N/A/*
2362N/A * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved.
0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
0N/A * under the terms of the GNU General Public License version 2 only, as
2362N/A * published by the Free Software Foundation. Oracle designates this
0N/A * particular file as subject to the "Classpath" exception as provided
2362N/A * by Oracle in the LICENSE file that accompanied this code.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0N/A *
2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
2362N/A * or visit www.oracle.com if you need additional information or have any
2362N/A * questions.
0N/A */
0N/A
0N/A/* __ieee754_acosh(x)
0N/A * Method :
0N/A * Based on
0N/A * acosh(x) = log [ x + sqrt(x*x-1) ]
0N/A * we have
0N/A * acosh(x) := log(x)+ln2, if x is large; else
0N/A * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
0N/A * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
0N/A *
0N/A * Special cases:
0N/A * acosh(x) is NaN with signal if x<1.
0N/A * acosh(NaN) is NaN without signal.
0N/A */
0N/A
0N/A#include "fdlibm.h"
0N/A
0N/A#ifdef __STDC__
0N/Astatic const double
0N/A#else
0N/Astatic double
0N/A#endif
0N/Aone = 1.0,
0N/Aln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */
0N/A
0N/A#ifdef __STDC__
0N/A double __ieee754_acosh(double x)
0N/A#else
0N/A double __ieee754_acosh(x)
0N/A double x;
0N/A#endif
0N/A{
0N/A double t;
0N/A int hx;
0N/A hx = __HI(x);
0N/A if(hx<0x3ff00000) { /* x < 1 */
0N/A return (x-x)/(x-x);
0N/A } else if(hx >=0x41b00000) { /* x > 2**28 */
0N/A if(hx >=0x7ff00000) { /* x is inf of NaN */
0N/A return x+x;
0N/A } else
0N/A return __ieee754_log(x)+ln2; /* acosh(huge)=log(2x) */
0N/A } else if(((hx-0x3ff00000)|__LO(x))==0) {
0N/A return 0.0; /* acosh(1) = 0 */
0N/A } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
0N/A t=x*x;
0N/A return __ieee754_log(2.0*x-one/(x+sqrt(t-one)));
0N/A } else { /* 1<x<2 */
0N/A t = x-one;
0N/A return log1p(t+sqrt(2.0*t+t*t));
0N/A }
0N/A}