Here you can find the source of atan2(double x, double y)
| Parameter | Description |
|---|---|
| x | a parameter |
| y | a parameter |
public static double atan2(double x, double y)
//package com.java2s; /*//w ww . j a v a 2 s. c o 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 atan2 function. Results are in the [0,2*PI) range. * * @param x * @param y * @return the calculated value */ public static double atan2(double x, double y) { // Origin - return zero if (y == 0.0 && x == 0.0) { return 0.0; } else if (x > 0.0) { if (y > 0.0) { // Point is in first quadrant return atan(y / x); } else { // Point is in fourth quadrant return 2 * Math.PI - atan(-y / x); } } else if (x < 0.0) { if (y < 0.0) { // Point is in third quadrant return Math.PI + atan(y / x); } else { // Point is in second quadrant return Math.PI - atan(-y / x); } } else if (y < 0.0) { // Special cases for when the point is directly on the Y axis. return 2 * Math.PI - Math.PI / 2.; } else { return Math.PI / 2.; } } /** * 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; } }