1 | |
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2 | /* @(#)s_sin.c 5.1 93/09/24 */ |
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3 | /* |
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4 | * ==================================================== |
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5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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6 | * |
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7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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8 | * Permission to use, copy, modify, and distribute this |
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9 | * software is freely granted, provided that this notice |
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10 | * is preserved. |
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11 | * ==================================================== |
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12 | */ |
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13 | |
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14 | /* |
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15 | FUNCTION |
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16 | <<sin>>, <<sinf>>, <<cos>>, <<cosf>>---sine or cosine |
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17 | INDEX |
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18 | sin |
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19 | INDEX |
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20 | sinf |
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21 | INDEX |
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22 | cos |
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23 | INDEX |
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24 | cosf |
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25 | SYNOPSIS |
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26 | #include <math.h> |
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27 | double sin(double <[x]>); |
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28 | float sinf(float <[x]>); |
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29 | double cos(double <[x]>); |
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30 | float cosf(float <[x]>); |
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31 | |
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32 | DESCRIPTION |
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33 | <<sin>> and <<cos>> compute (respectively) the sine and cosine |
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34 | of the argument <[x]>. Angles are specified in radians. |
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35 | |
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36 | <<sinf>> and <<cosf>> are identical, save that they take and |
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37 | return <<float>> values. |
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38 | |
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39 | |
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40 | RETURNS |
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41 | The sine or cosine of <[x]> is returned. |
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42 | |
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43 | PORTABILITY |
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44 | <<sin>> and <<cos>> are ANSI C. |
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45 | <<sinf>> and <<cosf>> are extensions. |
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46 | |
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47 | QUICKREF |
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48 | sin ansi pure |
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49 | sinf - pure |
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50 | */ |
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51 | |
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52 | /* sin(x) |
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53 | * Return sine function of x. |
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54 | * |
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55 | * kernel function: |
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56 | * __kernel_sin ... sine function on [-pi/4,pi/4] |
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57 | * __kernel_cos ... cose function on [-pi/4,pi/4] |
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58 | * __ieee754_rem_pio2 ... argument reduction routine |
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59 | * |
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60 | * Method. |
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61 | * Let S,C and T denote the sin, cos and tan respectively on |
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62 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 |
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63 | * in [-pi/4 , +pi/4], and let n = k mod 4. |
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64 | * We have |
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65 | * |
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66 | * n sin(x) cos(x) tan(x) |
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67 | * ---------------------------------------------------------- |
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68 | * 0 S C T |
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69 | * 1 C -S -1/T |
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70 | * 2 -S -C T |
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71 | * 3 -C S -1/T |
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72 | * ---------------------------------------------------------- |
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73 | * |
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74 | * Special cases: |
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75 | * Let trig be any of sin, cos, or tan. |
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76 | * trig(+-INF) is NaN, with signals; |
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77 | * trig(NaN) is that NaN; |
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78 | * |
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79 | * Accuracy: |
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80 | * TRIG(x) returns trig(x) nearly rounded |
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81 | */ |
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82 | |
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83 | #include "fdlibm.h" |
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84 | |
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85 | #ifndef _DOUBLE_IS_32BITS |
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86 | |
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87 | #ifdef __STDC__ |
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88 | double sin(double x) |
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89 | #else |
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90 | double sin(x) |
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91 | double x; |
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92 | #endif |
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93 | { |
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94 | double y[2],z=0.0; |
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95 | __int32_t n,ix; |
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96 | |
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97 | /* High word of x. */ |
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98 | GET_HIGH_WORD(ix,x); |
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99 | |
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100 | /* |x| ~< pi/4 */ |
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101 | ix &= 0x7fffffff; |
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102 | if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0); |
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103 | |
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104 | /* sin(Inf or NaN) is NaN */ |
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105 | else if (ix>=0x7ff00000) return x-x; |
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106 | |
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107 | /* argument reduction needed */ |
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108 | else { |
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109 | n = __ieee754_rem_pio2(x,y); |
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110 | switch(n&3) { |
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111 | case 0: return __kernel_sin(y[0],y[1],1); |
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112 | case 1: return __kernel_cos(y[0],y[1]); |
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113 | case 2: return -__kernel_sin(y[0],y[1],1); |
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114 | default: |
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115 | return -__kernel_cos(y[0],y[1]); |
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116 | } |
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117 | } |
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118 | } |
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119 | |
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120 | #endif /* _DOUBLE_IS_32BITS */ |
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