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9.7

Part of 1995 All-Russian Olympiad Regional Round

Problems(1)

concyclic, cuts of reg. hexagon All-Russian MO 1995 Regional (R4) 9.7

Source:

8/26/2024
A regular hexagon of side 55 is cut into unit equilateral triangles by lines parallel to the sides of the hexagon. We call the vertices of these triangles knots. If more than half of all knots are marked, show that there exist five marked knots that lie on a circle.
geometryConcyclichexagon