Euclid's+Elements

Euclid's Elements serve as the basis for all geometry. The link below is to a direct translation of all 13 books. The site contains interactive activities that demonstrate many of the propositions.

[|Euclid's Elements]

from http://unapologetic.wordpress.com/2009/02/13/lincolns-bicentennial/** It’s said that he carried three books with him, particularly as a young itinerant lawyer. The Bible is a given. A collection of Shakespeare isn’t unexpected, considering his practiced ease with language. But the third? Lincoln studied Euclid, and carried a copy of the //Elements//. His law partner tells of Lincoln stretched out on the floor, reading geometry in the lamplight. Lincoln himself explained his interest:
 * Lincoln's View of the Elements

In the course of my law reading I constantly came upon the word “demonstrate”. I thought at first that I understood its meaning, but soon became satisfied that I did not. I said to myself, What do I do when I demonstrate more than when I reason or prove? How does demonstration differ from any other proof? I consulted Webster’s Dictionary. They told of ‘certain proof,’ ‘proof beyond the possibility of doubt’; but I could form no idea of what sort of proof that was. I thought a great many things were proved beyond the possibility of doubt, without recourse to any such extraordinary process of reasoning as I understood demonstration to be. I consulted all the dictionaries and books of reference I could find, but with no better results. You might as well have defined blue to a blind man. At last I said,- Lincoln, you never can make a lawyer if you do not understand what demonstrate means; and I left my situation in Springfield, went home to my father’s house, and stayed there till I could give any proposition in the six books of Euclid at sight. I then found out what demonstrate means, and went back to my law studies.