k_tanf.c revision 152741
1/* k_tanf.c -- float version of k_tan.c 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5/* 6 * ==================================================== 7 * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. 8 * 9 * Permission to use, copy, modify, and distribute this 10 * software is freely granted, provided that this notice 11 * is preserved. 12 * ==================================================== 13 */ 14 15#ifndef INLINE_KERNEL_TANF 16#ifndef lint 17static char rcsid[] = "$FreeBSD: head/lib/msun/src/k_tanf.c 152741 2005-11-24 02:04:26Z bde $"; 18#endif 19#endif 20 21#include "math.h" 22#include "math_private.h" 23 24/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */ 25static const double 26T[] = { 27 0x15554d3418c99f.0p-54, /* 0.333331395030791399758 */ 28 0x1112fd38999f72.0p-55, /* 0.133392002712976742718 */ 29 0x1b54c91d865afe.0p-57, /* 0.0533812378445670393523 */ 30 0x191df3908c33ce.0p-58, /* 0.0245283181166547278873 */ 31 0x185dadfcecf44e.0p-61, /* 0.00297435743359967304927 */ 32 0x1362b9bf971bcd.0p-59, /* 0.00946564784943673166728 */ 33}; 34 35#ifdef INLINE_KERNEL_TANF 36extern inline 37#endif 38float 39__kernel_tandf(double x, int iy) 40{ 41 double z,r,v,w,s; 42 int32_t ix,hx; 43 44 GET_FLOAT_WORD(hx,x); 45 ix = hx&0x7fffffff; 46 z = x*x; 47 w = z*z; 48 /* Break x^5*(T[1]+x^2*T[2]+...) into 49 * x^5*(T[1]+x^4*T[3]+x^8*T[5]) + 50 * x^5*(x^2*(T[2]+x^4*T[4])) 51 */ 52 r = T[1]+w*(T[3]+w*T[5]); 53 v = z*(T[2]+w*T[4]); 54 s = z*x; 55 r = z*s*(r+v); 56 r += T[0]*s; 57 w = x+r; 58 if(iy==1) return w; 59 else return -1.0/w; 60} 61