1 /* @(#)s_cos.c 5.1 93/09/24 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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
10 * ====================================================
12 * $FreeBSD: src/lib/msun/src/s_cos.c,v 1.6 1999/08/28 00:06:46 peter Exp $
13 * $DragonFly: src/lib/msun/src/Attic/s_cos.c,v 1.3 2004/12/29 15:22:57 asmodai Exp $
17 * Return cosine function of x.
20 * __kernel_sin ... sine function on [-pi/4,pi/4]
21 * __kernel_cos ... cosine function on [-pi/4,pi/4]
22 * __ieee754_rem_pio2 ... argument reduction routine
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.
30 * n sin(x) cos(x) tan(x)
31 * ----------------------------------------------------------
36 * ----------------------------------------------------------
39 * Let trig be any of sin, cos, or tan.
40 * trig(+-INF) is NaN, with signals;
41 * trig(NaN) is that NaN;
44 * TRIG(x) returns trig(x) nearly rounded
48 #include "math_private.h"
51 __generic_cos(double x)
61 if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
63 /* cos(Inf or NaN) is NaN */
64 else if (ix>=0x7ff00000) return x-x;
66 /* argument reduction needed */
68 n = __ieee754_rem_pio2(x,y);
70 case 0: return __kernel_cos(y[0],y[1]);
71 case 1: return -__kernel_sin(y[0],y[1],1);
72 case 2: return -__kernel_cos(y[0],y[1]);
74 return __kernel_sin(y[0],y[1],1);