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6e953631 | 1 | /* s_tanl.c -- long double version of s_tan.c. |
abfbdde1 | 2 | * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz. |
6e953631 | 3 | */ |
9c84384c | 4 | |
abfbdde1 | 5 | /* @(#)s_tan.c 5.1 93/09/24 */ |
6e953631 UD |
6 | /* |
7 | * ==================================================== | |
8 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
9 | * | |
10 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
11 | * Permission to use, copy, modify, and distribute this | |
12 | * software is freely granted, provided that this notice | |
13 | * is preserved. | |
14 | * ==================================================== | |
15 | */ | |
16 | ||
6e953631 UD |
17 | /* tanl(x) |
18 | * Return tangent function of x. | |
19 | * | |
20 | * kernel function: | |
21 | * __kernel_tanl ... tangent function on [-pi/4,pi/4] | |
22 | * __ieee754_rem_pio2l ... argument reduction routine | |
23 | * | |
24 | * Method. | |
25 | * Let S,C and T denote the sin, cos and tan respectively on | |
26 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 | |
27 | * in [-pi/4 , +pi/4], and let n = k mod 4. | |
28 | * We have | |
29 | * | |
30 | * n sin(x) cos(x) tan(x) | |
31 | * ---------------------------------------------------------- | |
32 | * 0 S C T | |
33 | * 1 C -S -1/T | |
34 | * 2 -S -C T | |
35 | * 3 -C S -1/T | |
36 | * ---------------------------------------------------------- | |
37 | * | |
38 | * Special cases: | |
39 | * Let trig be any of sin, cos, or tan. | |
40 | * trig(+-INF) is NaN, with signals; | |
41 | * trig(NaN) is that NaN; | |
42 | * | |
43 | * Accuracy: | |
44 | * TRIG(x) returns trig(x) nearly rounded | |
45 | */ | |
46 | ||
7f3394bd | 47 | #include <errno.h> |
1ed0291c RH |
48 | #include <math.h> |
49 | #include <math_private.h> | |
6e953631 | 50 | |
8db21882 | 51 | long double __tanl(long double x) |
6e953631 | 52 | { |
abfbdde1 UD |
53 | long double y[2],z=0.0L; |
54 | int64_t n, ix; | |
6e953631 UD |
55 | |
56 | /* High word of x. */ | |
abfbdde1 | 57 | GET_LDOUBLE_MSW64(ix,x); |
6e953631 UD |
58 | |
59 | /* |x| ~< pi/4 */ | |
abfbdde1 UD |
60 | ix &= 0x7fffffffffffffffLL; |
61 | if(ix <= 0x3ffe921fb54442d1LL) return __kernel_tanl(x,z,1); | |
6e953631 | 62 | |
abfbdde1 | 63 | /* tanl(Inf or NaN) is NaN */ |
7f3394bd UD |
64 | else if (ix>=0x7fff000000000000LL) { |
65 | if (ix == 0x7fff000000000000LL) { | |
66 | GET_LDOUBLE_LSW64(n,x); | |
67 | if (n == 0) | |
68 | __set_errno (EDOM); | |
69 | } | |
70 | return x-x; /* NaN */ | |
71 | } | |
6e953631 UD |
72 | |
73 | /* argument reduction needed */ | |
74 | else { | |
75 | n = __ieee754_rem_pio2l(x,y); | |
76 | return __kernel_tanl(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even | |
77 | -1 -- n odd */ | |
78 | } | |
79 | } | |
80 | weak_alias (__tanl, tanl) |