Does inscribing a circle, then a triangle, then ..., inside of an initial triangle telescope to some "center" of that triangle?

by Mike Pierce   Last Updated April 25, 2018 16:20 PM

Start with a triangle, and construct its inscribed circle. Take the three points where the inscribed circle is tangent to the triangle, and construct a new triangle with those points as the vertices. Then construct the inscribed circle of this new triangle. Continuing this construction indefinitely gives us a sequence of inscribed circles and triangles that telescope down to a limit point. This is just the construction from this question, but we start with a triangle instead of a circle (and so no choice of points is being made).

In the comments Steven Stadnicki brought up a good question: does this construction telescope down to a defined center of the original triangle? By "defined center", I mean any of the many many points that have been given a name like prefixcenter of a triangle. It's naturally not the incenter, since the limit point will literally be the limit point of the incenters of the sequence of nested triangles, which isn't constant. It can't be the orthocenter or circumcenter since those could easily lie outside the triangle, and I checked that it's not the centroid.

I suppose an equivalent question would be: does there exist an alternative way to construct this limit point using only finitely many steps that maybe someone has considered before?



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