Euclid (c. 325-265 B.C.) studied at Plato's Academy in Athens, then later moved to Egypt [see map] where he taught mathematics at the Alexandrian school during the reign of the first of the Macedonian rulers, Ptolemy I Soter. Macedonians ruled in Egypt following Alexander the Great's conquests.
Euclid was an elder contemporary of Archimedes and Eratosthenes, according to Greek Geometry From Thales to Euclid, by George Johnston Allman. He says Euclid gathered together material from earlier mathematicians Eudoxus and Theaetetus and added thorough proofs that had been lacking.
Euclid is credited with having put together material from such earlier mathematicians, expanded it, and with having written an Elements, a text book containing teachings on algebra, number theory, and especially geometry. It is divided into 13 books, with plane geometry covered in Books I, II, II, IV, and VI; proportion, in Book V; the properties of numbers in VII, VIII, and IX; surd quantities in Book X; solid geometry in Book XII; and miscellaneous proposition in plane and solid geometry in Book XIII, according to Rubert Deakin in Euclid Book I. Allman credits Euclid with a quip that there is no royal road to geometry -- it just takes time to learn.
Euclid proved his concepts logically, using definitions, axioms, and postulates. Proclus Diadochus wrote a commentary on Euclid's Elements that kept Euclid's works in circulation.
Other works by Euclid are: Division of Figures, Data, Phaenomena, Optics, and three works that have not survived: Porisms, Surface Loci, and Pseudaria.
Euclid is on the list of Most Important People to Know in Ancient History.
* Source: Euclid, His Life and System, by Thomas Smith; (1902).