projects / uclibc-ng.git / blame
| Commit | Line | Data |
|---|---|---|
| 7ce331c0 EA |
1 | /* @(#)s_sin.c 5.1 93/09/24 */ |
| 2 | /* | |
| 3 | * ==================================================== | |
| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
| 5 | * | |
| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
| 7 | * Permission to use, copy, modify, and distribute this | |
| 8 | * software is freely granted, provided that this notice | |
| 9 | * is preserved. | |
| 10 | * ==================================================== | |
| 11 | */ | |
| 12 | ||
| 13 | #if defined(LIBM_SCCS) && !defined(lint) | |
| 14 | static char rcsid[] = "$NetBSD: s_sin.c,v 1.7 1995/05/10 20:48:15 jtc Exp $"; | |
| 15 | #endif | |
| 16 | ||
| 17 | /* sin(x) | |
| 18 | * Return sine function of x. | |
| 19 | * | |
| 20 | * kernel function: | |
| 21 | * __kernel_sin ... sine function on [-pi/4,pi/4] | |
| 22 | * __kernel_cos ... cose function on [-pi/4,pi/4] | |
| 23 | * __ieee754_rem_pio2 ... argument reduction routine | |
| 24 | * | |
| 25 | * Method. | |
| 26 | * Let S,C and T denote the sin, cos and tan respectively on | |
| 27 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 | |
| 28 | * in [-pi/4 , +pi/4], and let n = k mod 4. | |
| 29 | * We have | |
| 30 | * | |
| 31 | * n sin(x) cos(x) tan(x) | |
| 32 | * ---------------------------------------------------------- | |
| 33 | * 0 S C T | |
| 34 | * 1 C -S -1/T | |
| 35 | * 2 -S -C T | |
| 36 | * 3 -C S -1/T | |
| 37 | * ---------------------------------------------------------- | |
| 38 | * | |
| 39 | * Special cases: | |
| 40 | * Let trig be any of sin, cos, or tan. | |
| 41 | * trig(+-INF) is NaN, with signals; | |
| 42 | * trig(NaN) is that NaN; | |
| 43 | * | |
| 44 | * Accuracy: | |
| 45 | * TRIG(x) returns trig(x) nearly rounded | |
| 46 | */ | |
| 47 | ||
| 48 | #include "math.h" | |
| 49 | #include "math_private.h" | |
| 50 | ||
| 51 | #ifdef __STDC__ | |
| 52 | double sin(double x) | |
| 53 | #else | |
| 54 | double sin(x) | |
| 55 | double x; | |
| 56 | #endif | |
| 57 | { | |
| 58 | double y[2],z=0.0; | |
| 59 | int32_t n, ix; | |
| 60 | ||
| 61 | /* High word of x. */ | |
| 62 | GET_HIGH_WORD(ix,x); | |
| 63 | ||
| 64 | /* |x| ~< pi/4 */ | |
| 65 | ix &= 0x7fffffff; | |
| 66 | if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0); | |
| 67 | ||
| 68 | /* sin(Inf or NaN) is NaN */ | |
| 69 | else if (ix>=0x7ff00000) return x-x; | |
| 70 | ||
| 71 | /* argument reduction needed */ | |
| 72 | else { | |
| 73 | n = __ieee754_rem_pio2(x,y); | |
| 74 | switch(n&3) { | |
| 75 | case 0: return __kernel_sin(y[0],y[1],1); | |
| 76 | case 1: return __kernel_cos(y[0],y[1]); | |
| 77 | case 2: return -__kernel_sin(y[0],y[1],1); | |
| 78 | default: | |
| 79 | return -__kernel_cos(y[0],y[1]); | |
| 80 | } | |
| 81 | } | |
| 82 | } |