2 /* @(#)s_tan.c 1.3 95/01/18 */
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
11 * ====================================================
15 * Return tangent function of x.
18 * __kernel_tan ... tangent function on [-pi/4,pi/4]
19 * __ieee754_rem_pio2 ... argument reduction routine
22 * Let S,C and T denote the sin, cos and tan respectively on
23 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
24 * in [-pi/4 , +pi/4], and let n = k mod 4.
27 * n sin(x) cos(x) tan(x)
28 * ----------------------------------------------------------
33 * ----------------------------------------------------------
36 * Let trig be any of sin, cos, or tan.
37 * trig(+-INF) is NaN, with signals;
38 * trig(NaN) is that NaN;
41 * TRIG(x) returns trig(x) nearly rounded
46 #ifndef _DOUBLE_IS_32BITS
63 if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
65 /* tan(Inf or NaN) is NaN */
66 else if (ix>=0x7ff00000) return x-x; /* NaN */
68 /* argument reduction needed */
70 n = __ieee754_rem_pio2(x,y);
71 return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
75 #endif /* _DOUBLE_IS_32BITS */