Problem

Source: 2023 Austrian Mathematical Olympiad , Junior Regional Competition , Problem 2

Tags: geometry, collinear, hexagon



Let $ABCDEF$ be a regular hexagon with sidelength s. The points $P$ and $Q$ are on the diagonals $BD$ and $DF$, respectively, such that $BP = DQ = s$. Prove that the three points $C$, $P$ and $Q$ are on a line. (Walther Janous)