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 * ====================================================
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static const char rcsid[] =
15 "$NetBSD: s_cos.c,v 1.7 1995/05/10 20:47:02 jtc Exp $";
19 * Return cosine function of x.
22 * __kernel_sin ... sine function on [-pi/4,pi/4]
23 * __kernel_cos ... cosine function on [-pi/4,pi/4]
24 * __ieee754_rem_pio2 ... argument reduction routine
27 * Let S,C and T denote the sin, cos and tan respectively on
28 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
29 * in [-pi/4 , +pi/4], and let n = k mod 4.
32 * n sin(x) cos(x) tan(x)
33 * ----------------------------------------------------------
38 * ----------------------------------------------------------
41 * Let trig be any of sin, cos, or tan.
42 * trig(+-INF) is NaN, with signals;
43 * trig(NaN) is that NaN;
46 * TRIG(x) returns trig(x) nearly rounded
49 #include "math_libm.h"
50 #include "math_private.h"
52 libm_hidden_proto(cos)
69 return __kernel_cos(x, z);
71 /* cos(Inf or NaN) is NaN */
72 else if (ix >= 0x7ff00000)
75 /* argument reduction needed */
77 n = __ieee754_rem_pio2(x, y);
80 return __kernel_cos(y[0], y[1]);
82 return -__kernel_sin(y[0], y[1], 1);
84 return -__kernel_cos(y[0], y[1]);
86 return __kernel_sin(y[0], y[1], 1);