diff options
author | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 19:29:30 -0800 |
---|---|---|
committer | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 19:29:30 -0800 |
commit | b07e1d9fd8d9e4e03698e0bd9bf77154c5390326 (patch) | |
tree | 87dbea36a0e5ed0f2f8e2a499b9c1014af6a38b5 /s_cos.c | |
parent | f177c949113889342d74aee8011a86bd4f589841 (diff) | |
download | fdlibm-b07e1d9fd8d9e4e03698e0bd9bf77154c5390326.tar.gz |
auto import from //depot/cupcake/@135843
Diffstat (limited to 's_cos.c')
-rw-r--r-- | s_cos.c | 78 |
1 files changed, 78 insertions, 0 deletions
@@ -0,0 +1,78 @@ + +/* @(#)s_cos.c 1.3 95/01/18 */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunSoft, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* ieee_cos(x) + * Return cosine function of x. + * + * kernel function: + * __kernel_sin ... sine function on [-pi/4,pi/4] + * __kernel_cos ... cosine function on [-pi/4,pi/4] + * __ieee754_rem_pio2 ... argument reduction routine + * + * Method. + * Let S,C and T denote the sin, cos and tan respectively on + * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 + * in [-pi/4 , +pi/4], and let n = k mod 4. + * We have + * + * n ieee_sin(x) ieee_cos(x) ieee_tan(x) + * ---------------------------------------------------------- + * 0 S C T + * 1 C -S -1/T + * 2 -S -C T + * 3 -C S -1/T + * ---------------------------------------------------------- + * + * Special cases: + * Let trig be any of sin, cos, or tan. + * trig(+-INF) is NaN, with signals; + * trig(NaN) is that NaN; + * + * Accuracy: + * TRIG(x) returns trig(x) nearly rounded + */ + +#include "fdlibm.h" + +#ifdef __STDC__ + double ieee_cos(double x) +#else + double ieee_cos(x) + double x; +#endif +{ + double y[2],z=0.0; + int n, ix; + + /* High word of x. */ + ix = __HI(x); + + /* |x| ~< pi/4 */ + ix &= 0x7fffffff; + if(ix <= 0x3fe921fb) return __kernel_cos(x,z); + + /* ieee_cos(Inf or NaN) is NaN */ + else if (ix>=0x7ff00000) return x-x; + + /* argument reduction needed */ + else { + n = __ieee754_rem_pio2(x,y); + switch(n&3) { + case 0: return __kernel_cos(y[0],y[1]); + case 1: return -__kernel_sin(y[0],y[1],1); + case 2: return -__kernel_cos(y[0],y[1]); + default: + return __kernel_sin(y[0],y[1],1); + } + } +} |