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Find the max number of points of intersection of semicircles

Source: P7: BWM 2014

October 7, 2014
functioncombinatorics proposedcombinatorics

Problem Statement

A line gg is given in a plane. nn distinct points are chosen arbitrarily from gg and are named as A1,A2,,AnA_1, A_2, \ldots, A_n. For each pair of points Ai,AjA_i,A_j, a semicircle is drawn with AiA_i and AjA_j as its endpoints. All semicircles lie on the same side of gg. Determine the maximum number of points (which are not lying in gg) of intersection of semicircles as a function of nn.