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#include <sys/cdefs.h>
14__FBSDID("$FreeBSD$");
15
16/* sin(x)
17 * Return sine function of x.
18 *
19 * kernel function:
20 *	__kernel_sin		... sine function on [-pi/4,pi/4]
21 *	__kernel_cos		... cose function on [-pi/4,pi/4]
22 *	__ieee754_rem_pio2	... argument reduction routine
23 *
24 * Method.
25 *      Let S,C and T denote the sin, cos and tan respectively on
26 *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
27 *	in [-pi/4 , +pi/4], and let n = k mod 4.
28 *	We have
29 *
30 *          n        sin(x)      cos(x)        tan(x)
31 *     ----------------------------------------------------------
32 *	    0	       S	   C		 T
33 *	    1	       C	  -S		-1/T
34 *	    2	      -S	  -C		 T
35 *	    3	      -C	   S		-1/T
36 *     ----------------------------------------------------------
37 *
38 * Special cases:
39 *      Let trig be any of sin, cos, or tan.
40 *      trig(+-INF)  is NaN, with signals;
41 *      trig(NaN)    is that NaN;
42 *
43 * Accuracy:
44 *	TRIG(x) returns trig(x) nearly rounded
45 */
46
47#include <float.h>
48
49#include "math.h"
50#define INLINE_REM_PIO2
51#include "math_private.h"
52#include "e_rem_pio2.c"
53
54double
55sin(double x)
56{
57	double y[2],z=0.0;
58	int32_t n, ix;
59
60    /* High word of x. */
61	GET_HIGH_WORD(ix,x);
62
63    /* |x| ~< pi/4 */
64	ix &= 0x7fffffff;
65	if(ix <= 0x3fe921fb) {
66	    if(ix<0x3e500000)			/* |x| < 2**-26 */
67	       {if((int)x==0) return x;}	/* generate inexact */
68	    return __kernel_sin(x,z,0);
69	}
70
71    /* sin(Inf or NaN) is NaN */
72	else if (ix>=0x7ff00000) return x-x;
73
74    /* argument reduction needed */
75	else {
76	    n = __ieee754_rem_pio2(x,y);
77	    switch(n&3) {
78		case 0: return  __kernel_sin(y[0],y[1],1);
79		case 1: return  __kernel_cos(y[0],y[1]);
80		case 2: return -__kernel_sin(y[0],y[1],1);
81		default:
82			return -__kernel_cos(y[0],y[1]);
83	    }
84	}
85}
86
87#if (LDBL_MANT_DIG == 53)
88__weak_reference(sin, sinl);
89#endif
90