Java atan2 atan2(double y, double x)

Description

atan

License

Open Source License

Declaration

static public double atan2(double y, double x) 

Method Source Code

//package com.java2s;
/**//from  w w  w .j av  a  2s  . c o  m
 * <p>Title: Class for float-point calculations in J2ME applications CLDC 1.1</p>
 * <p>Description: Useful methods for float-point calculations which absent in native Math class</p>
 * <p>Copyright: Copyright (c) 2004 Nick Henson</p>
 * <p>Company: UNTEH</p>
 * <p>License: Free use only for non-commercial purpose</p>
 * <p>If you want to use all or part of this class for commercial applications then take into account these conditions:</p>
 * <p>1. I need a one copy of your product which includes my class with license key and so on</p>
 * <p>2. Please append my copyright information henson.midp.Float (C) by Nikolay Klimchuk on ?About? screen of your product</p>
 * <p>3. If you have web site please append link <a href=?http://henson.newmail.ru?>Nikolay Klimchuk</a> on the page with description of your product</p>
 * <p>That's all, thank you!</p>
 * @author Nikolay Klimchuk http://henson.newmail.ru
 * @version 0.5
 */

public class Main {
    /** Square root from 3 */
    final static public double SQRT3 = 1.732050807568877294;

    static public double atan2(double y, double x) {
        // if x=y=0
        if (y == 0. && x == 0.)
            return 0.;
        // if x>0 atan(y/x)
        if (x > 0.)
            return atan(y / x);
        // if x<0 sign(y)*(pi - atan(|y/x|))
        if (x < 0.) {
            if (y < 0.)
                return -(Math.PI - atan(y / x));
            else
                return Math.PI - atan(-y / x);
        }
        // if x=0 y!=0 sign(y)*pi/2
        if (y < 0.)
            return -Math.PI / 2.;
        else
            return Math.PI / 2.;
    }

    static public double atan(double x) {
        boolean signChange = false;
        boolean Invert = false;
        int sp = 0;
        double x2, a;
        // check up the sign change
        if (x < 0.) {
            x = -x;
            signChange = true;
        }
        // check up the invertation
        if (x > 1.) {
            x = 1 / x;
            Invert = true;
        }
        // process shrinking the domain until x<PI/12
        while (x > Math.PI / 12) {
            sp++;
            a = x + SQRT3;
            a = 1 / a;
            x = x * SQRT3;
            x = x - 1;
            x = x * a;
        }
        // calculation core
        x2 = x * x;
        a = x2 + 1.4087812;
        a = 0.55913709 / a;
        a = a + 0.60310579;
        a = a - (x2 * 0.05160454);
        a = a * x;
        // process until sp=0
        while (sp > 0) {
            a = a + Math.PI / 6;
            sp--;
        }
        // invertation took place
        if (Invert)
            a = Math.PI / 2 - a;
        // sign change took place
        if (signChange)
            a = -a;
        //
        return a;
    }
}

Related

1. atan2(double arg1, double arg2)
2. atan2(double x, double y)
3. atan2(double y, double x)
4. atan2(double y, double x)
5. atan2(double y, double x)
6. atan2(double[] arr1, double[] arr2)
7. atan2(final double y, final double x)
8. atan2(float y, float x)