TOT 008 1981 Spring J2 almost centre of symmetry
Source:
August 17, 2019
symmetrygeometrygeometric transformation
Problem Statement
is a finite set of points in a plane. Point in the plane is called an “almost centre of symmetry” of set if it is possible to remove from one point in such a way that among the remaining members is the centre of symmetry in the usual sense. How many such “almost centres of symmetry” may a finite point set in a plane have? Indicate all such points.(V Prasolov, Moscow)