MathDB
Bohemian vertices of a convex polygon

Source: 2019 MEMO Problem I-2

August 29, 2019
combinatorial geometrycombinatoricsMEMO 2019memo

Problem Statement

Let n3n\geq 3 be an integer. We say that a vertex Ai(1in)A_i (1\leq i\leq n) of a convex polygon A1A2AnA_1A_2 \dots A_n is Bohemian if its reflection with respect to the midpoint of Ai1Ai+1A_{i-1}A_{i+1} (with A0=AnA_0=A_n and A1=An+1A_1=A_{n+1}) lies inside or on the boundary of the polygon A1A2AnA_1A_2\dots A_n. Determine the smallest possible number of Bohemian vertices a convex nn-gon can have (depending on nn).
Proposed by Dominik Burek, Poland