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8.4

Part of 1998 All-Russian Olympiad Regional Round

Problems(1)

n points lie on 2 circles - All-Russian MO 1998 Regional (R4) 8.4

Source:

9/17/2024
A set of n≥9n\ge 9 points is given on the plane. For any 9 it points can be selected from all circles so that all these points end up on selected circles. Prove that all n points lie on two circles
geometrycombinatoricscombinatorial geometry