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Stony Brook, Spring 2005

This page contains syllabus and problems of the workshop WSE187 (Spring 2005) in mathematics organized by Dusa McDuff and Valentina Kiritchenko. In this workshop, we explore constructions using a compass and a ruler. What regular n-gons can be constructed using only a compass and a ruler? Since complex numbers are essential for solving this problem we review complex numbers and some of their applications. For instance, using complex numbers we show that the regular 5-gon is constructible, but the regular 7-gon is not. And how to construct a regular 15-gon?
The picture by Dr. Reza Sarhangi (taken from MSRI web site) describes the construction of a regular 17-gon. The famous mathematician Carl Friedrich Gauss (1777-1855) discovered this construction in 1796 when he was eighteen years old.
Construction of regular 17-gon

February 17,22
We explore some basic constructions using a compass and a ruler. We construct an equilateral triangle, a square and a regular octagon. We show that if lengths 1, a and b are constructible, then so are ab, a/b and the square root of a.

February 24, March 1
We study complex numbers and their relation to regular polygons. We see how solving the equation x^5=1 helps to construct a regular pentagon.

March 3,8
Projects