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 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