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