Home | History | Annotate | Line # | Download | only in noieee_src 
      1  1.5    agc /*	$NetBSD: n_tan.c,v 1.5 2003/08/07 16:44:52 agc Exp $	*/
      2  1.1  ragge /*
      3  1.1  ragge  * Copyright (c) 1987, 1993
      4  1.1  ragge  *	The Regents of the University of California.  All rights reserved.
      5  1.1  ragge  *
      6  1.1  ragge  * Redistribution and use in source and binary forms, with or without
      7  1.1  ragge  * modification, are permitted provided that the following conditions
      8  1.1  ragge  * are met:
      9  1.1  ragge  * 1. Redistributions of source code must retain the above copyright
     10  1.1  ragge  *    notice, this list of conditions and the following disclaimer.
     11  1.1  ragge  * 2. Redistributions in binary form must reproduce the above copyright
     12  1.1  ragge  *    notice, this list of conditions and the following disclaimer in the
     13  1.1  ragge  *    documentation and/or other materials provided with the distribution.
     14  1.5    agc  * 3. Neither the name of the University nor the names of its contributors
     15  1.1  ragge  *    may be used to endorse or promote products derived from this software
     16  1.1  ragge  *    without specific prior written permission.
     17  1.1  ragge  *
     18  1.1  ragge  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     19  1.1  ragge  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     20  1.1  ragge  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     21  1.1  ragge  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     22  1.1  ragge  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  1.1  ragge  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     24  1.1  ragge  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  1.1  ragge  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  1.1  ragge  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  1.1  ragge  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  1.1  ragge  * SUCH DAMAGE.
     29  1.1  ragge  */
     30  1.1  ragge 
     31  1.1  ragge #ifndef lint
     32  1.2  ragge #if 0
     33  1.1  ragge static char sccsid[] = "@(#)tan.c	8.1 (Berkeley) 6/4/93";
     34  1.2  ragge #endif
     35  1.1  ragge #endif /* not lint */
     36  1.1  ragge 
     37  1.1  ragge #include "mathimpl.h"
     38  1.1  ragge #include "trig.h"
     39  1.1  ragge double
     40  1.4   matt tan(double x)
     41  1.1  ragge {
     42  1.1  ragge 	double a,z,ss,cc,c;
     43  1.1  ragge 	int k;
     44  1.1  ragge 
     45  1.1  ragge 	if(!finite(x))		/* tan(NaN) and tan(INF) must be NaN */
     46  1.1  ragge 		return x-x;
     47  1.1  ragge 	x = drem(x,PI);			/* reduce x into [-PI/2, PI/2] */
     48  1.4   matt 	a = copysign(x,__one);		/* ... = abs(x) */
     49  1.1  ragge 	if (a >= PIo4) {
     50  1.1  ragge 		k = 1;
     51  1.1  ragge 		x = copysign(PIo2-a,x);
     52  1.1  ragge 	}
     53  1.1  ragge 	else {
     54  1.1  ragge 		k = 0;
     55  1.4   matt 		if (a < __small) {
     56  1.4   matt 			z=__big+a;
     57  1.1  ragge 			return x;
     58  1.1  ragge 		}
     59  1.1  ragge 	}
     60  1.1  ragge 	z = x*x;
     61  1.1  ragge 	cc = cos__C(z);
     62  1.1  ragge 	ss = sin__S(z);
     63  1.4   matt 	z *= __half;			/* Next get c = cos(x) accurately */
     64  1.4   matt 	c = (z >= thresh ? __half-((z-__half)-cc) : __one-(z-cc));
     65  1.1  ragge 	if (k == 0)
     66  1.1  ragge 		return x+(x*(z-(cc-ss)))/c;	/* ... sin/cos */
     67  1.1  ragge #ifdef national
     68  1.4   matt 	else if (x == __zero)
     69  1.1  ragge 		return copysign(fmax,x);	/* no inf on 32k */
     70  1.1  ragge #endif	/* national */
     71  1.1  ragge 	else
     72  1.1  ragge 		return c/(x+x*ss);		/* ... cos/sin */
     73  1.1  ragge }
     74