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2aa62f2b | 1 | /* @(#)s_cos.c 5.1 93/09/24 */\r |
2 | /*\r | |
3 | * ====================================================\r | |
4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r | |
5 | *\r | |
6 | * Developed at SunPro, a Sun Microsystems, Inc. business.\r | |
7 | * Permission to use, copy, modify, and distribute this\r | |
8 | * software is freely granted, provided that this notice\r | |
9 | * is preserved.\r | |
10 | * ====================================================\r | |
11 | */\r | |
12 | #include <LibConfig.h>\r | |
13 | #include <sys/EfiCdefs.h>\r | |
14 | #if defined(LIBM_SCCS) && !defined(lint)\r | |
15 | __RCSID("$NetBSD: s_cos.c,v 1.10 2002/05/26 22:01:54 wiz Exp $");\r | |
16 | #endif\r | |
17 | \r | |
18 | /* cos(x)\r | |
19 | * Return cosine function of x.\r | |
20 | *\r | |
21 | * kernel function:\r | |
22 | * __kernel_sin ... sine function on [-pi/4,pi/4]\r | |
23 | * __kernel_cos ... cosine function on [-pi/4,pi/4]\r | |
24 | * __ieee754_rem_pio2 ... argument reduction routine\r | |
25 | *\r | |
26 | * Method.\r | |
27 | * Let S,C and T denote the sin, cos and tan respectively on\r | |
28 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2\r | |
29 | * in [-pi/4 , +pi/4], and let n = k mod 4.\r | |
30 | * We have\r | |
31 | *\r | |
32 | * n sin(x) cos(x) tan(x)\r | |
33 | * ----------------------------------------------------------\r | |
34 | * 0 S C T\r | |
35 | * 1 C -S -1/T\r | |
36 | * 2 -S -C T\r | |
37 | * 3 -C S -1/T\r | |
38 | * ----------------------------------------------------------\r | |
39 | *\r | |
40 | * Special cases:\r | |
41 | * Let trig be any of sin, cos, or tan.\r | |
42 | * trig(+-INF) is NaN, with signals;\r | |
43 | * trig(NaN) is that NaN;\r | |
44 | *\r | |
45 | * Accuracy:\r | |
46 | * TRIG(x) returns trig(x) nearly rounded\r | |
47 | */\r | |
48 | \r | |
49 | #include "math.h"\r | |
50 | #include "math_private.h"\r | |
51 | \r | |
52 | double\r | |
53 | cos(double x)\r | |
54 | {\r | |
55 | double y[2],z=0.0;\r | |
56 | int32_t n, ix;\r | |
57 | \r | |
58 | /* High word of x. */\r | |
59 | GET_HIGH_WORD(ix,x);\r | |
60 | \r | |
61 | /* |x| ~< pi/4 */\r | |
62 | ix &= 0x7fffffff;\r | |
63 | if(ix <= 0x3fe921fb) return __kernel_cos(x,z);\r | |
64 | \r | |
65 | /* cos(Inf or NaN) is NaN */\r | |
66 | else if (ix>=0x7ff00000) return x-x;\r | |
67 | \r | |
68 | /* argument reduction needed */\r | |
69 | else {\r | |
70 | n = __ieee754_rem_pio2(x,y);\r | |
71 | switch(n&3) {\r | |
72 | case 0: return __kernel_cos(y[0],y[1]);\r | |
73 | case 1: return -__kernel_sin(y[0],y[1],1);\r | |
74 | case 2: return -__kernel_cos(y[0],y[1]);\r | |
75 | default:\r | |
76 | return __kernel_sin(y[0],y[1],1);\r | |
77 | }\r | |
78 | }\r | |
79 | }\r |