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sould policemen know geometry? a criminal problem

Source: Sharygin Geometry Olympiad 2016 Final Round problem 8 grade 8

July 22, 2018
geometryproblem

Problem Statement

A criminal is at point XX, and three policemen at points A,BA, B and CC block him up, i.e. the point XX lies inside the triangle ABCABC. Each evening one of the policemen is replaced in the following way: a new policeman takes the position equidistant from three former policemen, after this one of the former policemen goes away so that three remaining policemen block up the criminal too. May the policemen after some time occupy again the points A,BA, B and CC (it is known that at any moment XX does not lie on a side of the triangle)?
by V.Protasov