1 /* s_cosl.c -- long double version of s_cos.c.
2 */
3
4 /*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15 /* cosl(x)
16 * Return cosine function of x.
17 *
18 * kernel function:
19 * __kernel_sinl ... sine function on [-pi/4,pi/4]
20 * __kernel_cosl ... cosine function on [-pi/4,pi/4]
21 * __ieee754_rem_pio2l ... argument reduction routine
22 *
23 * Method.
24 * Let S,C and T denote the sin, cos and tan respectively on
25 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
26 * in [-pi/4 , +pi/4], and let n = k mod 4.
27 * We have
28 *
29 * n sin(x) cos(x) tan(x)
30 * ----------------------------------------------------------
31 * 0 S C T
32 * 1 C -S -1/T
33 * 2 -S -C T
34 * 3 -C S -1/T
35 * ----------------------------------------------------------
36 *
37 * Special cases:
38 * Let trig be any of sin, cos, or tan.
39 * trig(+-INF) is NaN, with signals;
40 * trig(NaN) is that NaN;
41 *
42 * Accuracy:
43 * TRIG(x) returns trig(x) nearly rounded
44 */
45
46 #include <errno.h>
47 #include <math.h>
48 #include <math_private.h>
49 #include <math_ldbl_opt.h>
50
__cosl(long double x)51 long double __cosl(long double x)
52 {
53 long double y[2],z=0.0L;
54 int64_t n, ix;
55 double xhi;
56
57 /* High word of x. */
58 xhi = ldbl_high (x);
59 EXTRACT_WORDS64 (ix, xhi);
60
61 /* |x| ~< pi/4 */
62 ix &= 0x7fffffffffffffffLL;
63 if(ix <= 0x3fe921fb54442d18LL)
64 return __kernel_cosl(x,z);
65
66 /* cos(Inf or NaN) is NaN */
67 else if (ix>=0x7ff0000000000000LL) {
68 if (ix == 0x7ff0000000000000LL)
69 __set_errno (EDOM);
70 return x-x;
71 }
72 /* argument reduction needed */
73 else {
74 n = __ieee754_rem_pio2l(x,y);
75 switch(n&3) {
76 case 0:
77 return __kernel_cosl(y[0],y[1]);
78 case 1:
79 return -__kernel_sinl(y[0],y[1],1);
80 case 2:
81 return -__kernel_cosl(y[0],y[1]);
82 default:
83 return __kernel_sinl(y[0],y[1],1);
84 }
85 }
86 }
87 long_double_symbol (libm, __cosl, cosl);
88