Law of Haversine
==============================
https://www.movable-type.co.uk/scripts/latlong.html
        private static final int EARTH_RADIUS = 6371000;  // meters
        double dLat = Math.toRadians(that.lat - this.lat);
        double dLon = Math.toRadians(that.lon - this.lon);
        double a = Math.sin(dLat / 2.0) * Math.sin(dLat / 2.0) +
                Math.cos(Math.toRadians(this.lat)) * Math.cos(Math.toRadians(that.lat)) *
                        Math.sin(dLon / 2.0) * Math.sin(dLon / 2.0);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
        return EARTH_RADIUS * c;

The haversine formula1 ‘remains particularly well-conditioned for numerical computa­tion even at small distances’ – 


1.2.30 Generate 5 random numbers
============================
read 5 int values, print average


1.2.34 3-sort
=============================
Read 3 integer command-line arguments, print in sorted order.
Use Math.min(), Math.max()
no if statements

5. Type conversion.

CMYK to RGB
============================
https://stackoverflow.com/questions/4858131/rgb-to-cmyk-and-back-algorithm

define white = ...

   public static int[] cmykToRgb(int cyan, int magenta, int yellow, int black)
    {
        if (black!=255) {
            int R = ((255-cyan) * (255-black)) / 255; 
            int G = ((255-magenta) * (255-black)) / 255; 
            int B = ((255-yellow) * (255-black)) / 255;
            return new int[] {R,G,B};
        } else {
            int R = 255 - cyan;
            int G = 255 - magenta;
            int B = 255 - yellow;
            return new int[] {R,G,B};
        }
    }


Projectile motion formulas
======================================
https://en.wikipedia.org/wiki/Projectile_motion