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3

Part of 1985 Poland - Second Round

Problems(1)

side of a convex quadrilateral, from vertices of regualr 195-gon

Source: Polish MO Recond Round 1985 p3

9/9/2024
Let L L be the set of all polylines ABCDA ABCDA , where A,B,C,D A, B, C, D are different vertices of a fixed regular 19851985 -gon. We randomly select a polyline from the set LL. Calculate the probability that it is the side of a convex quadrilateral.
combinatoricscombinatorial geometrygeometry