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 * tanl(x) 32 * Table look-up algorithm by K.C. Ng, November, 1989. 33 * 34 * kernel function: 35 * __k_tanl ... tangent function on [-pi/4,pi/4] 36 * __rem_pio2l ... argument reduction routine 37 * 38 * Method. 39 * Let S and C denote the sin and cos respectively on [-PI/4, +PI/4]. 40 * 1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in 41 * [-pi/2 , +pi/2], and let n = k mod 4. 42 * 2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have 43 * 44 * n sin(x) cos(x) tan(x) 45 * ---------------------------------------------------------- 46 * 0 S C S/C 47 * 1 C -S -C/S 48 * 2 -S -C S/C 49 * 3 -C S -C/S 50 * ---------------------------------------------------------- 51 * 52 * Special cases: 53 * Let trig be any of sin, cos, or tan. 54 * trig(+-INF) is NaN, with signals; 55 * trig(NaN) is that NaN; 56 * 57 * Accuracy: 58 * computer TRIG(x) returns trig(x) nearly rounded. 59 */ 60 61 #pragma weak __tanl = tanl 62 63 #include "libm.h" 64 #include "longdouble.h" 65 66 long double 67 tanl(long double x) { 68 long double y[2], z = 0.0L; 69 int n, ix; 70 71 ix = *(int *) &x; /* High word of x */ 72 ix &= 0x7fffffff; 73 if (ix <= 0x3ffe9220) /* |x| ~< pi/4 */ 74 return (__k_tanl(x, z, 0)); 75 else if (ix >= 0x7fff0000) /* trig(Inf or NaN) is NaN */ 76 return (x - x); 77 else { /* argument reduction needed */ 78 n = __rem_pio2l(x, y); 79 return (__k_tanl(y[0], y[1], (n & 1))); 80 } 81 } 82