Java atan atan(double arg)

Description

atan

License

Open Source License

Declaration

public static double atan(double arg) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    static final double sq2p1 = 2.414213562373095048802e0;
    static final double sq2m1 = .414213562373095048802e0;
    static final double p4 = .161536412982230228262e2;
    static final double p3 = .26842548195503973794141e3;
    static final double p2 = .11530293515404850115428136e4;
    static final double p1 = .178040631643319697105464587e4;
    static final double p0 = .89678597403663861959987488e3;
    static final double q4 = .5895697050844462222791e2;
    static final double q3 = .536265374031215315104235e3;
    static final double q2 = .16667838148816337184521798e4;
    static final double q1 = .207933497444540981287275926e4;
    static final double q0 = .89678597403663861962481162e3;
    static final double PIO2 = 1.5707963267948966135E0;

    public static double atan(double arg) {
        if (arg > 0) {
            return msatan(arg);
        }//w ww  . j  a  v a  2  s .  c o m
        return -msatan(-arg);
    }

    private static double msatan(double arg) {
        if (arg < sq2m1) {
            return mxatan(arg);
        }
        if (arg > sq2p1) {
            return PIO2 - mxatan(1 / arg);
        }
        return PIO2 / 2 + mxatan((arg - 1) / (arg + 1));
    }

    private static double mxatan(double arg) {
        double argsq, value;

        argsq = arg * arg;
        value = ((((p4 * argsq + p3) * argsq + p2) * argsq + p1) * argsq + p0);
        value = value / (((((argsq + q4) * argsq + q3) * argsq + q2) * argsq + q1) * argsq + q0);
        return value * arg;
    }
}

Related

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