MathDB
set closed under orthocenter

Source: IMOC 2017 C5

August 13, 2021
geometrycombinatoricscombinatorial geometry

Problem Statement

We say a finite set SS of points with ∣S∣≥3|S|\ge3 is good if for any three distinct elements of SS, they are non-collinear and the orthocenter of them is also in SS. Find all good sets.
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