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Lines and Circles on a Plane

Source: Canadian Mathematical Olympiad - 1981 - Problem 3.

May 27, 2011
combinatorics unsolvedcombinatorics

Problem Statement

Given a finite collection of lines in a plane PP, show that it is possible to draw an arbitrarily large circle in PP which does not meet any of them. On the other hand, show that it is possible to arrange a countable infinite sequence of lines (first line, second line, third line, etc.) in PP so that every circle in PP meets at least one of the lines. (A point is not considered to be a circle.)