lib/libm/common/sincos.c

/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)sincos.c    5.5 (Berkeley) 10/9/90";
#endif /* not lint */

#include "trig.h"
double
sin(x)
double x;
{
        double a,c,z;

        if(!finite(x))          /* sin(NaN) and sin(INF) must be NaN */
                return x-x;
        x=drem(x,PI2);          /* reduce x into [-PI,PI] */
        a=copysign(x,one);
        if (a >= PIo4) {
                if(a >= PI3o4)          /* ... in [3PI/4,PI] */
                        x = copysign((a = PI-a),x);
                else {                  /* ... in [PI/4,3PI/4]  */
                        a = PIo2-a;             /* rtn. sign(x)*C(PI/2-|x|) */
                        z = a*a;
                        c = cos__C(z);
                        z *= half;
                        a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
                        return copysign(a,x);
                }
        }

        if (a < small) {                /* rtn. S(x) */
                big+a;
                return x;
        }
        a = x*x;
        return x+x*sin__S(a);
}

double
cos(x)
double x;
{
        double a,c,z,s = 1.0;

        if(!finite(x))          /* cos(NaN) and cos(INF) must be NaN */
                return x-x;
        x=drem(x,PI2);          /* reduce x into [-PI,PI] */
        a=copysign(x,one);
        if (a >= PIo4) {
                if (a >= PI3o4) {       /* ... in [3PI/4,PI] */
                        a = PI-a;
                        s = negone;
                }
                else {                  /* ... in [PI/4,3PI/4] */
                        a = PIo2-a;
                        c = a*a;
                        return a+a*sin__S(c);   /* rtn. S(PI/2-|x|) */
                }
        }
        if (a < small) {
                big+a;
                return s;               /* rtn. s*C(a) */
        }
        z = a*a;
        c = cos__C(z);
        z *= half;
        a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
        return copysign(a,s);
}