1 /* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
13 * ====================================================
17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/k_tanf.c,v 1.5 1999/08/28 00:06:42 peter Exp $";
21 #include "math_private.h"
27 one = 1.0000000000e+00, /* 0x3f800000 */
28 pio4 = 7.8539812565e-01, /* 0x3f490fda */
29 pio4lo= 3.7748947079e-08, /* 0x33222168 */
31 3.3333334327e-01, /* 0x3eaaaaab */
32 1.3333334029e-01, /* 0x3e088889 */
33 5.3968254477e-02, /* 0x3d5d0dd1 */
34 2.1869488060e-02, /* 0x3cb327a4 */
35 8.8632395491e-03, /* 0x3c11371f */
36 3.5920790397e-03, /* 0x3b6b6916 */
37 1.4562094584e-03, /* 0x3abede48 */
38 5.8804126456e-04, /* 0x3a1a26c8 */
39 2.4646313977e-04, /* 0x398137b9 */
40 7.8179444245e-05, /* 0x38a3f445 */
41 7.1407252108e-05, /* 0x3895c07a */
42 -1.8558637748e-05, /* 0xb79bae5f */
43 2.5907305826e-05, /* 0x37d95384 */
47 float __kernel_tanf(float x, float y, int iy)
49 float __kernel_tanf(x, y, iy)
56 ix = hx&0x7fffffff; /* high word of |x| */
57 if(ix<0x31800000) /* x < 2**-28 */
58 {if((int)x==0) { /* generate inexact */
59 if((ix|(iy+1))==0) return one/fabsf(x);
60 else return (iy==1)? x: -one/x;
63 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
64 if(hx<0) {x = -x; y = -y;}
71 /* Break x^5*(T[1]+x^2*T[2]+...) into
72 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
73 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
75 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
76 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
78 r = y + z*(s*(r+v)+y);
83 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
86 else { /* if allow error up to 2 ulp,
87 simply return -1.0/(x+r) here */
88 /* compute -1.0/(x+r) accurately */
93 SET_FLOAT_WORD(z,i&0xfffff000);
94 v = r-(z - x); /* z+v = r+x */
95 t = a = -(float)1.0/w; /* a = -1.0/w */
97 SET_FLOAT_WORD(t,i&0xfffff000);