A regular Polygon
of an even number of sides being inscribed in a circle as
ABC...A'...C'B'A' so that AA' is a diameter if two angular
points next but one to each other as B, B' be joined, and
the other lines parallel to BB' and joining pairs of angular
points be drawn as CC', DD',...., then
(BB' + CC' +.... ) / AA' = A'B / BA
