1 /* @(#)s_tan.c 5.1 93/09/24 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
14 static char rcsid[] = "$FreeBSD$";
18 * Return tangent function of x.
21 * __kernel_tan ... tangent function on [-pi/4,pi/4]
22 * __ieee754_rem_pio2 ... argument reduction routine
25 * Let S,C and T denote the sin, cos and tan respectively on
26 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
27 * in [-pi/4 , +pi/4], and let n = k mod 4.
30 * n sin(x) cos(x) tan(x)
31 * ----------------------------------------------------------
36 * ----------------------------------------------------------
39 * Let trig be any of sin, cos, or tan.
40 * trig(+-INF) is NaN, with signals;
41 * trig(NaN) is that NaN;
44 * TRIG(x) returns trig(x) nearly rounded
48 #include "math_private.h"
61 if(ix <= 0x3fe921fb) {
62 if(ix<0x3e300000) /* x < 2**-28 */
63 if((int)x==0) return x; /* generate inexact */
64 return __kernel_tan(x,z,1);
67 /* tan(Inf or NaN) is NaN */
68 else if (ix>=0x7ff00000) return x-x; /* NaN */
70 /* argument reduction needed */
72 n = __ieee754_rem_pio2(x,y);
73 return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even