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n_sincos.c revision 1.2 
      1 /*	$NetBSD: n_sincos.c,v 1.2 1998/08/22 12:49:09 ragge Exp $	*/
      2 /*
      3  * Copyright (c) 1987, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. All advertising materials mentioning features or use of this software
     15  *    must display the following acknowledgement:
     16  *	This product includes software developed by the University of
     17  *	California, Berkeley and its contributors.
     18  * 4. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #ifndef lint
     36 #if 0
     37 static char sccsid[] = "@(#)sincos.c	8.1 (Berkeley) 6/4/93";
     38 #endif
     39 #endif /* not lint */
     40 
     41 #include "mathimpl.h"
     42 #include "trig.h"
     43 double
     44 sin(x)
     45 double x;
     46 {
     47 	double a,c,z;
     48 
     49         if(!finite(x))		/* sin(NaN) and sin(INF) must be NaN */
     50 		return x-x;
     51 	x=drem(x,PI2);		/* reduce x into [-PI,PI] */
     52 	a=copysign(x,one);
     53 	if (a >= PIo4) {
     54 		if(a >= PI3o4)		/* ... in [3PI/4,PI] */
     55 			x = copysign((a = PI-a),x);
     56 		else {			/* ... in [PI/4,3PI/4]  */
     57 			a = PIo2-a;		/* rtn. sign(x)*C(PI/2-|x|) */
     58 			z = a*a;
     59 			c = cos__C(z);
     60 			z *= half;
     61 			a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
     62 			return copysign(a,x);
     63 		}
     64 	}
     65 
     66 	if (a < small) {		/* rtn. S(x) */
     67 		z = big+a;
     68 		return x;
     69 	}
     70 	return x+x*sin__S(x*x);
     71 }
     72 
     73 double
     74 cos(x)
     75 double x;
     76 {
     77 	double a,c,z,s = 1.0;
     78 
     79 	if(!finite(x))		/* cos(NaN) and cos(INF) must be NaN */
     80 		return x-x;
     81 	x=drem(x,PI2);		/* reduce x into [-PI,PI] */
     82 	a=copysign(x,one);
     83 	if (a >= PIo4) {
     84 		if (a >= PI3o4) {	/* ... in [3PI/4,PI] */
     85 			a = PI-a;
     86 			s = negone;
     87 		}
     88 		else {			/* ... in [PI/4,3PI/4] */
     89 			a = PIo2-a;
     90 			return a+a*sin__S(a*a);	/* rtn. S(PI/2-|x|) */
     91 		}
     92 	}
     93 	if (a < small) {
     94 		z = big+a;
     95 		return s;		/* rtn. s*C(a) */
     96 	}
     97 	z = a*a;
     98 	c = cos__C(z);
     99 	z *= half;
    100 	a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
    101 	return copysign(a,s);
    102 }
    103