This function returns an approximated value of sin using the taylor approximation of power 5. - Java java.lang

Java examples for java.lang:Math Calculation

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Description

This function returns an approximated value of sin using the taylor approximation of power 5.

Demo Code

/*/* w  w w.  j  a  v  a  2  s  .  com*/
 * Created on 02-May-2006 at 17:31:01.
 * 
 * Copyright (c) 2010 Robert Virkus / Enough Software
 *
 * This file is part of J2ME Polish.
 *
 * J2ME Polish is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * J2ME Polish is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with J2ME Polish; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * Commercial licenses are also available, please
 * refer to the accompanying LICENSE.txt or visit
 * http://www.j2mepolish.org for details.
 */
//package com.java2s;

public class Main {
    /**
     * This function returns an approximated value of sin using the taylor
     *    approximation of power 5. Please keep in mind that the input angle
     *    is NOT measured in degree or radian. It is measured in 1000, which
     *  equals 2 * PI. Therefore you have to convert degree via 'd*1000/360'
     *  and radian via 'r*1000/2/PI'.
     *  On top of that the resulting value equals sin()*1000 to avoid doubling
     *  point errors.
     *  Keep also in mind that this approximation is not necessary
     *  monotonically increasing (especially around apxSin=1000).
     *
     * @param x1k this is the angle 360 degree correspond to 1000.
     * @return sin()*1000
     */
    public static int apxSin(int x1k) {
        int p = 1;
        x1k = x1k % 1000;

        if (x1k < 0) {
            x1k += 1000;
        }

        if (x1k > 250) {
            if (x1k < 500) {
                x1k = 500 - x1k;
            } else {
                if (x1k < 750) {
                    p = -1;
                    x1k = x1k - 500;
                } else {
                    p = -1;
                    x1k = 1000 - x1k;
                }
            }
        }

        x1k = (x1k * 3141 * 2) / 1000;

        int sq = x1k * x1k / 1000;
        long ret = x1k * 1000000 + x1k * (-sq / 6 * 1000 + sq * sq / 120);

        return (int) (ret / 1005000) * p;
    }
}

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