Java atan atan(double x)

Description

Approximates the atan function.

License

Open Source License

Parameter

Parameter	Description
x	a parameter

Return

the calculated value

Declaration

public static double atan(double x) 

Method Source Code

//package com.java2s;
/*// ww  w. j  a va2  s  . co m
 * 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.
 */

public class Main {
    /**
     * Approximates the atan function. Uses a polynomial approximation that should
     * be accurate enough for most practical purposes.
     * 
     * @param x
     * @return the calculated value
     */
    public static double atan(double x) {
        double res;

        if (Math.abs(x) < 1) {
            res = x / (1 + 0.28 * x * x);
        } else {
            // NOTE : Due to some weird JVM behavior,
            // if x is negative it's more accurate to calculate
            // atan for -x and then negate it, rather than calculate atan
            // for x directly.
            if (x < 0.0) {
                x = -x;
                res = (Math.PI / 2 - x / (x * x + 0.28));
                res = -res;
            } else {
                res = (Math.PI / 2 - x / (x * x + 0.28));
            }
        }

        return res;
    }
}

Related

1. atan(double a)
2. atan(double a)
3. atan(double arg)
4. atan(float tan_value)
5. atan(float value)
6. atan(float x)
7. atan(int f)