1. The radius of a small circle is determined by the angular measure of the line from the centre of the earth. E.g. radius of 50 degrees north or south is 6370cos 50.
2. The distance between the two points is given by the angle difference between the lines of longitudes divided by three hundred and sixty multiplied by pie multiplied by the diameter of the circle.
D=x/360 x 3.142 X 2 x 6370cosA.