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 /*
31 * arccosin function
32 * ________
33 * / 1 - x
34 * acos(x) = 2*atan2( / -------- , 1 )
35 * \/ 1 + x
36 *
37 * ________
38 * / 1 - x
39 * = 2*atan ( / -------- ) for non-exceptional x.
40 * \/ 1 + x
41 *
42 * Special cases:
43 * if x is NaN, return x itself;
44 * if |x|>1, return NaN with invalid signal.
45 */
46
47 #pragma weak __acosl = acosl
48
49 #include "libm.h"
50
51 static const long double zero = 0.0L, one = 1.0L;
52
53 long double
acosl(long double x)54 acosl(long double x) {
55 if (isnanl(x))
56 return (x + x);
57 else if (fabsl(x) < one)
58 x = atanl(sqrtl((one - x) / (one + x)));
59 else if (x == -one)
60 x = atan2l(one, zero); /* x <- PI */
61 else if (x == one)
62 x = zero;
63 else { /* |x| > 1 create invalid signal */
64 return (zero / zero);
65 }
66 return (x + x);
67 }
68