k_tanf.c revision 152870 
1/* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 * Optimized by Bruce D. Evans.
4 */
5
6/*
7 * ====================================================
8 * Copyright 2004 Sun Microsystems, Inc.  All Rights Reserved.
9 *
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#ifndef INLINE_KERNEL_TANDF
17#ifndef lint
18static char rcsid[] = "$FreeBSD: head/lib/msun/src/k_tanf.c 152870 2005-11-28 05:35:32Z bde $";
19#endif
20#endif
21
22#include "math.h"
23#include "math_private.h"
24
25/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */
26static const double
27T[] =  {
28  0x15554d3418c99f.0p-54,	/* 0.333331395030791399758 */
29  0x1112fd38999f72.0p-55,	/* 0.133392002712976742718 */
30  0x1b54c91d865afe.0p-57,	/* 0.0533812378445670393523 */
31  0x191df3908c33ce.0p-58,	/* 0.0245283181166547278873 */
32  0x185dadfcecf44e.0p-61,	/* 0.00297435743359967304927 */
33  0x1362b9bf971bcd.0p-59,	/* 0.00946564784943673166728 */
34};
35
36#ifdef INLINE_KERNEL_TANDF
37extern inline
38#endif
39float
40__kernel_tandf(double x, int iy)
41{
42	double z,r,w,s;
43
44	z	=  x*x;
45	w 	=  z*z;
46    /* Break x^5*(T[1]+x^2*T[2]+...) into
47     *	  x^5*(T[1]+x^4*T[3]+x^8*T[5]) +
48     *	  x^5*(x^2*(T[2]+x^4*T[4]))
49     */
50	r = (T[1]+w*(T[3]+w*T[5])) + z*(T[2]+w*T[4]);
51	s = z*x;
52	r = (x+s*T[0])+(s*z)*r;
53	if(iy==1) return r;
54	else return -1.0/r;
55}
56