MathDB
The set T of triangles

Source: Baltic Way 2002

November 13, 2010
combinatorics proposedcombinatorics

Problem Statement

Let PP be a set of n≥3n\ge 3 points in the plane, no three of which are on a line. How many possibilities are there to choose a set TT of (n−12)\binom{n-1}{2} triangles, whose vertices are all in PP, such that each triangle in TT has a side that is not a side of any other triangle in TT?
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