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 * ====================================================
14 static char rcsid[] = "$FreeBSD$";
18 * Return cosine function of x.
21 * __kernel_sin ... sine function on [-pi/4,pi/4]
22 * __kernel_cos ... cosine function on [-pi/4,pi/4]
23 * __ieee754_rem_pio2 ... argument reduction routine
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.
31 * n sin(x) cos(x) tan(x)
32 * ----------------------------------------------------------
37 * ----------------------------------------------------------
40 * Let trig be any of sin, cos, or tan.
41 * trig(+-INF) is NaN, with signals;
42 * trig(NaN) is that NaN;
45 * TRIG(x) returns trig(x) nearly rounded
49 #include "math_private.h"
62 if(ix <= 0x3fe921fb) {
63 if(ix<0x3e400000) /* if x < 2**-27 */
64 if(((int)x)==0) return 1.0; /* generate inexact */
65 return __kernel_cos(x,z);
68 /* cos(Inf or NaN) is NaN */
69 else if (ix>=0x7ff00000) return x-x;
71 /* argument reduction needed */
73 n = __ieee754_rem_pio2(x,y);
75 case 0: return __kernel_cos(y[0],y[1]);
76 case 1: return -__kernel_sin(y[0],y[1],1);
77 case 2: return -__kernel_cos(y[0],y[1]);
79 return __kernel_sin(y[0],y[1],1);