some conic constructions

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Hi all;
Attached are two constructios for a conic (parabola, hyperbola, ellipse) 
given 5 points which lie on it.
The first, braik_conic.geo, follows the Braikenridge-Maclaurin 
(http://mathworld.wolfram.com/Braikenridge-MaclaurinConstruction.html) 
construction exactly, with the circle around X serving only as a means 
to vary the line.
The second file, steiner_conic.geo, creates the same conic but using the 
Steiner definition of a conic as a projectivity between two pencils. 
Here, the parameter Z is bound only to the line A2C1.
Under certain conditions, there are gaps in the conics, but they are 
generally negligible.
Enjoy!
Marcel

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