OpenCores
URL https://opencores.org/ocsvn/or1k/or1k/trunk

Subversion Repositories or1k

[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [s_tan.c] - Blame information for rev 39

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 39 lampret
 
2
/* @(#)s_tan.c 5.1 93/09/24 */
3
/*
4
 * ====================================================
5
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6
 *
7
 * Developed at SunPro, a Sun Microsystems, Inc. business.
8
 * Permission to use, copy, modify, and distribute this
9
 * software is freely granted, provided that this notice
10
 * is preserved.
11
 * ====================================================
12
 */
13
 
14
 
15
/*
16
 
17
FUNCTION
18
        <<tan>>, <<tanf>>---tangent
19
 
20
INDEX
21
tan
22
INDEX
23
tanf
24
 
25
ANSI_SYNOPSIS
26
        #include <math.h>
27
        double tan(double <[x]>);
28
        float tanf(float <[x]>);
29
 
30
TRAD_SYNOPSIS
31
        #include <math.h>
32
        double tan(<[x]>)
33
        double <[x]>;
34
 
35
        float tanf(<[x]>)
36
        float <[x]>;
37
 
38
 
39
DESCRIPTION
40
<<tan>> computes the tangent of the argument <[x]>.
41
Angles are specified in radians.
42
 
43
<<tanf>> is identical, save that it takes and returns <<float>> values.
44
 
45
RETURNS
46
The tangent of <[x]> is returned.
47
 
48
PORTABILITY
49
<<tan>> is ANSI. <<tanf>> is an extension.
50
*/
51
 
52
/* tan(x)
53
 * Return tangent function of x.
54
 *
55
 * kernel function:
56
 *      __kernel_tan            ... tangent function on [-pi/4,pi/4]
57
 *      __ieee754_rem_pio2      ... argument reduction routine
58
 *
59
 * Method.
60
 *      Let S,C and T denote the sin, cos and tan respectively on
61
 *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
62
 *      in [-pi/4 , +pi/4], and let n = k mod 4.
63
 *      We have
64
 *
65
 *          n        sin(x)      cos(x)        tan(x)
66
 *     ----------------------------------------------------------
67
 *          0          S           C             T
68
 *          1          C          -S            -1/T
69
 *          2         -S          -C             T
70
 *          3         -C           S            -1/T
71
 *     ----------------------------------------------------------
72
 *
73
 * Special cases:
74
 *      Let trig be any of sin, cos, or tan.
75
 *      trig(+-INF)  is NaN, with signals;
76
 *      trig(NaN)    is that NaN;
77
 *
78
 * Accuracy:
79
 *      TRIG(x) returns trig(x) nearly rounded
80
 */
81
 
82
#include "fdlibm.h"
83
 
84
#ifndef _DOUBLE_IS_32BITS
85
 
86
#ifdef __STDC__
87
        double tan(double x)
88
#else
89
        double tan(x)
90
        double x;
91
#endif
92
{
93
        double y[2],z=0.0;
94
        __int32_t n,ix;
95
 
96
    /* High word of x. */
97
        GET_HIGH_WORD(ix,x);
98
 
99
    /* |x| ~< pi/4 */
100
        ix &= 0x7fffffff;
101
        if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
102
 
103
    /* tan(Inf or NaN) is NaN */
104
        else if (ix>=0x7ff00000) return x-x;            /* NaN */
105
 
106
    /* argument reduction needed */
107
        else {
108
            n = __ieee754_rem_pio2(x,y);
109
            return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
110
                                                        -1 -- n odd */
111
        }
112
}
113
 
114
#endif /* _DOUBLE_IS_32BITS */

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.