5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
87 lines
2.1 KiB
C
87 lines
2.1 KiB
C
/* @(#)s_sin.c 5.1 93/09/24 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
#if defined(LIBM_SCCS) && !defined(lint)
|
|
__RCSID("$NetBSD: s_sin.c,v 1.11 2007/08/20 16:01:39 drochner Exp $");
|
|
#endif
|
|
|
|
/* sin(x)
|
|
* Return sine function of x.
|
|
*
|
|
* kernel function:
|
|
* __kernel_sin ... sine function on [-pi/4,pi/4]
|
|
* __kernel_cos ... cose function on [-pi/4,pi/4]
|
|
* __ieee754_rem_pio2 ... argument reduction routine
|
|
*
|
|
* Method.
|
|
* Let S,C and T denote the sin, cos and tan respectively on
|
|
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
|
|
* in [-pi/4 , +pi/4], and let n = k mod 4.
|
|
* We have
|
|
*
|
|
* n sin(x) cos(x) tan(x)
|
|
* ----------------------------------------------------------
|
|
* 0 S C T
|
|
* 1 C -S -1/T
|
|
* 2 -S -C T
|
|
* 3 -C S -1/T
|
|
* ----------------------------------------------------------
|
|
*
|
|
* Special cases:
|
|
* Let trig be any of sin, cos, or tan.
|
|
* trig(+-INF) is NaN, with signals;
|
|
* trig(NaN) is that NaN;
|
|
*
|
|
* Accuracy:
|
|
* TRIG(x) returns trig(x) nearly rounded
|
|
*/
|
|
|
|
#include "namespace.h"
|
|
#include "math.h"
|
|
#include "math_private.h"
|
|
|
|
#if 0 /* notyet */
|
|
#ifdef __weak_alias
|
|
__weak_alias(sin, _sin)
|
|
#endif
|
|
#endif
|
|
|
|
double
|
|
sin(double x)
|
|
{
|
|
double y[2],z=0.0;
|
|
int32_t n, ix;
|
|
|
|
/* High word of x. */
|
|
GET_HIGH_WORD(ix,x);
|
|
|
|
/* |x| ~< pi/4 */
|
|
ix &= 0x7fffffff;
|
|
if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0);
|
|
|
|
/* sin(Inf or NaN) is NaN */
|
|
else if (ix>=0x7ff00000) return x-x;
|
|
|
|
/* argument reduction needed */
|
|
else {
|
|
n = __ieee754_rem_pio2(x,y);
|
|
switch(n&3) {
|
|
case 0: return __kernel_sin(y[0],y[1],1);
|
|
case 1: return __kernel_cos(y[0],y[1]);
|
|
case 2: return -__kernel_sin(y[0],y[1],1);
|
|
default:
|
|
return -__kernel_cos(y[0],y[1]);
|
|
}
|
|
}
|
|
}
|