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Subject: "degenerate case of Pascal's theorem"     Previous Topic | Next Topic
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Conferences The CTK Exchange College math Topic #256
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John A. Velling
May-01-02, 05:18 AM (EST)
"degenerate case of Pascal's theorem"
   Consider the degenerate case of Pascal's theorem when vertices A and B, and vertices D and E, respectively, merge. The figure from the proof given on this site degenerates into a figure inscribed in a circle. For simplicity say we have points A, B, C, and D arranged cyclically on the circle, and the six lines tA =tangent at A, AB, BC, tC =tangent at C, CD and DA. Can we somehow adapt the proof of Pascal's theorem to show that
X = tA * tC
Y = AB * CD and
Z = BC * DA
are collinear? (* means intersection here) I am trying to construct a proof of this fact using only classical tools and there are very few tools available to prove colinearity of three points.

John A. Velling

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