Author: Laurence D. Finston
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Last updated: August 27, 2010
|Pascal's Theorem and the Braikenridge-Maclaurin Construction|
The GNU 3DLDF language has a data type for each of the conic sections: ellipse, circle, parabola, and hyperbola. Each of these data types corresponds to a class in the C++ code. Ellipse and Circle were both part of 3DLDF from the very first release, and each has a fairly complete set of functions and parser rules. I haven't yet created web pages for them, but they are documented in the The 3DLDF User and Reference Manual for Release 18.104.22.168. Of course, the parser rules for ellipse and circle are not documented in the manual, because it predates the parser.
The types parabola and hyperbola are more recent. I
have written web pages for them, but the sets of functions and parser
rules for them are still incomplete. Nor are parabola and hyperbola
bullet-proof as ellipse and circle yet.
The Braikenridge-Maclaurin construction is a method of finding any number of points on a conic section given five points on the curve.
The following examples (in the files braik_01.* and braik_02.*)
use the 3DLDF language to make drawings illustrating the
Braikenridge-Maclaurin construction. They were written before I'd
programmed the data type conic_section_lattice the operations
that can be applied to objects of this type, in particular
get_point . See below for an example demonstrating the use of
|GNU 3DLDF code:|| braik_01.ldf
|TeX code:|| braik_01.txt
|PDF file:|| braik_01.pdf
|PostScript file:|| braik_01.ps
|Compressed (gzipped) PostScript file:|| braik_01.ps.gz
|GNU 3DLDF code:|| braik_02.ldf
|TeX code:|| braik_02.txt
|PDF file:|| braik_02.pdf
|Compressed (gzipped) PDF file:|| braik_02.pdf.gz
|PostScript file:|| braik_02.ps
|Compressed (gzipped) PostScript file:|| braik_02.ps.gz
The following example uses the get_point operation applied to a conic_section_lattice object to find the points on the conic section. In this case, it's an ellipse, but the Braikenridge-Maclaurin construction works for any conic section.
lattice makes it possible to keep the intersection
points X, Y, and Z within the boundaries of the
ellipse. With a parabola or hyperbola, this isn't possible for the
two extreme points, but it's still useful for trying to keep the
interesection points and the point found on the curve within
|GNU 3DLDF code:|| braik_03.ldf
|TeX code:|| braik_03.txt
|PDF file:|| braik_03.pdf
|Compressed (gzipped) PDF file:|| braik_03.pdf.gz
|PostScript file:|| braik_03.ps
|Compressed (gzipped) PostScript file:|| braik_03.ps.gz