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 Discussion: Pantograph tool Topic: pantograph Related Item: http://mathforum.org/mathtools/tool/894/

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 Subject: RE: pantograph Author: stek Date: Feb 16 2009
Hi,

If you have Sketchpad, Cabri, etc. available, you can construct one very easily.
The simple solution is to use a transformation: Dilate point A relative to fixed
point B, creating dilated point C. Then drag point A and trace point C. The
scale factor for the dilation determines the amount of stretching or shrinking
that occurs. Use a negative scale factor to put the image on the opposite side
of B.

Modeling an actual physical pantograph rules out dilation, and so requires a
Euclidean construction. This is a bit more complex; the basic idea is to use a
construction, based on similar triangles, that fixes the lengths of the bars.
(These fixed-length bars are constructed using a
circle-by-center-and-radius construction so that they are free to pivot
while remaining fixed in length.)

Let me know if you want the details of the construction. (If you have either