Date: Jun 6, 2013 10:25 PM
Author: Brian Q. Hutchings
Subject: Conic eccentricity through five points

cool problem; I knew about 5 points defining a conic,
but not that it was related to those coeffs., duh.

> Find eccentricity of a conic in terms of 5 points
(x1,y1) to (x5,y5); as there are 5 constants
in  a x^2 + 2 h x y + b y^2 + 2 f x + 2 g y  = 1.