Java acos acos(double x)

Description

acos

License

Open Source License

Declaration

static public double acos(double x) 

Method Source Code

//package com.java2s;
/**/*from w  ww.  j  a v  a 2s .co  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 acos(double x) {
        double f = asin(x);
        if (f == Double.NaN)
            return f;
        return Math.PI / 2 - f;
    }

    static public double asin(double x) {
        if (x < -1. || x > 1.)
            return Double.NaN;
        if (x == -1.)
            return -Math.PI / 2;
        if (x == 1)
            return Math.PI / 2;
        return atan(x / Math.sqrt(1 - x * x));
    }

    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. acos(double a)
2. acos(double a)
3. acos(double d)
4. acos(double x)
5. acos(final float a)
6. acos(float value)
7. acos(float value)