IMO Shortlist 1971 problem 2
Dodao/la:
arhiva2. travnja 2012. Prove that for every positive integer
we can find a finite set
of points in the plane, such that given any point
of
, there are exactly
points in
at unit distance from
.
%V0
Prove that for every positive integer $m$ we can find a finite set $S$ of points in the plane, such that given any point $A$ of $S$, there are exactly $m$ points in $S$ at unit distance from $A$.
Izvor: Međunarodna matematička olimpijada, shortlist 1971