Collapsible Compass

Date: 01/23/2002 at 12:12:48
From: Shane Hecox
Subject: Collapsible compass

My question is: How did the early Greek mathematicians reproduce 
lengths with a collapsible compass? I can't find any information on 
how they did this. All I find are statements saying that when the 
compass is picked up it acts as if it collapses.

Date: 01/23/2002 at 12:26:55
From: Doctor Wilkinson
Subject: Re: Collapsible compass

This is an excellent question, Shane! This construction is 
Proposition 2 of Euclid's _Elements_ and is as beautiful today 
as it was 2500 years ago. You can look at it at:

   Book I, Proposition 2 (Euclid's Elements - David Joyce)
   http://aleph0.clarku.edu/~djoyce/java/elements/bookI/propI2.html   

- Doctor Wilkinson, The Math Forum
  http://mathforum.org/dr.math/