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Subject: "Circumcircle/Incircle Question"     Previous Topic | Next Topic
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Conferences The CTK Exchange College math Topic #576
Reading Topic #576
Bractals
Member since Jun-9-03
Jul-02-06, 08:01 PM (EST)
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"Circumcircle/Incircle Question"
 
   I'm looking for a synthetic proof for the following.

Let P and Q be the circumcircle and incircle respectively of an arbitrary triangle. If ABC is a triangle inscribed in P with AB and AC tangent to Q, then BC is tangent to Q.


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alexb
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1855 posts
Jul-05-06, 08:11 PM (EST)
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1. "RE: Circumcircle/Incircle Question"
In response to message #0
 
   What do you mean by synthetic? One way or another you have to establish a certain relationship between the radii of P and Q and the distance between their centers. This is Poncelet's Porism for a 3-gon. See https://mathworld.wolfram.com/PonceletsPorism.html.


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Bractals
Member since Jun-9-03
Jul-06-06, 04:52 AM (EST)
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2. "RE: Circumcircle/Incircle Question"
In response to message #1
 
   Thanks for the reference.


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