1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
24 */
25/*
26 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
27 * Use is subject to license terms.
28 */
29
30#pragma weak __acoshl = acoshl
31
32#include "libm.h"
33
34static const long double
35	zero	= 0.0L,
36	ln2	= 6.931471805599453094172321214581765680755e-0001L,
37	one	= 1.0L,
38	big	= 1.e+20L;
39
40long double
41acoshl(long double x) {
42	long double t;
43
44	if (isnanl(x))
45		return (x + x);
46	else if (x > big)
47		return (logl(x) + ln2);
48	else if (x > one) {
49		t = sqrtl(x - one);
50		return (log1pl(t * (t + sqrtl(x + one))));
51	} else if (x == one)
52		return (zero);
53	else
54		return ((x - x) / (x - x));
55}
56