From: "David Petry" Subject: Re: ruler and compass constructions Date: Wed, 5 Jan 2000 09:22:50 -0800 Newsgroups: sci.math Summary: Archimedes sliding-ruler trisection Bill Taylor wrote >I was quite blown away by the utter simplicity and effectiveness >of the Archimedes sliding-ruler trisection, when I first saw it. >It's as near as dammit to a fully Euclidean construction... you need >a magnifying glass to tell it isn't one! I first saw the sliding-ruler trisection, using a marked ruler, when I was taking high school geometry. It was in our textbook. I had to discover for myself that the sliding ruler trisection can be done with an unmarked ruler. That is, you can simulate a marked ruler by holding the points of the compass next to the unmarked ruler. What blew me away about that was the realization that the assertion that you can't trisect an angle with just a compass and an unmarked straight edge is quite literally wrong. To make the assertion correct, you need to add restrictions on the proper use of the compass and straight edge.