## Day 20: Elements XIII

### Summary

Euclid's construction of regular polyhedra.

Presentation and discussion of propositions from Book XIII.

Pay particular attention to Propositions 5 and 12-17.

Introduction to number theory in Euclid.

### Reading

Euclid *Elements* XIII. Heath's version is on
reserve, or you may look at David Joyce's Elements
on the web.

J. Fauvel and J.Gray, *The History of Mathematics,* Chapter 3.

V.J. Katz, *A History of Mathematics,* Section 2.4.

### Links

Illustration of the five
regular solids.

### Homework

Analysis of assigned proposition.

On to Day 21.

Up to Ancient
and
Classical Mathematics

Last modified: 2 November 2005

Duncan J. Melville

Comments to dmelville@stlawu.edu