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 * ====================================================
12 * $FreeBSD: src/lib/msun/src/s_tan.c,v 1.6 1999/08/28 00:06:56 peter Exp $
13 * $DragonFly: src/lib/msun/src/Attic/s_tan.c,v 1.2 2003/06/17 04:26:53 dillon Exp $
17 * Return tangent function of x.
20 * __kernel_tan ... tangent function on [-pi/4,pi/4]
21 * __ieee754_rem_pio2 ... argument reduction routine
24 * Let S,C and T denote the sin, cos and tan respectively on
25 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
26 * in [-pi/4 , +pi/4], and let n = k mod 4.
29 * n sin(x) cos(x) tan(x)
30 * ----------------------------------------------------------
35 * ----------------------------------------------------------
38 * Let trig be any of sin, cos, or tan.
39 * trig(+-INF) is NaN, with signals;
40 * trig(NaN) is that NaN;
43 * TRIG(x) returns trig(x) nearly rounded
47 #include "math_private.h"
50 double __generic_tan(double x)
52 double __generic_tan(x)
64 if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
66 /* tan(Inf or NaN) is NaN */
67 else if (ix>=0x7ff00000) return x-x; /* NaN */
69 /* argument reduction needed */
71 n = __ieee754_rem_pio2(x,y);
72 return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even