Theon of Alexandria Theon of Alexandria Theon of Alexandria (; ; 335 – c. 405) was a Greek scholar and mathematician who lived in Alexandria, Egypt. He edited and arranged Euclid's "Elements" and wrote commentaries on works by Euclid and Ptolemy. His daughter Hypatia also won fame as a mathematician. Little is known about the life of Theon. He made predictions and observances of solar and lunar eclipses in 364 which show he was active at that time, and he is said to have lived during the reign of Theodosius I (379–395). The biographical tradition of the tenth century Byzantine "Suda" defines Theon
Library of Alexandria largest and most significant libraries of the ancient world, but details about it are a mixture of history and legend. The earliest known surviving source of information on the founding of the Library of Alexandria is the pseudepigraphic "Letter of Aristeas", which was composed between 180 and 145 BC. The "Letter of Aristeas" claims that the Library was founded during the reign of Ptolemy I Soter ( 323– 283 BC) and that it was initially organized by Demetrius of Phalerum, a student of Aristotle who had been exiled from Athens and taken refuge in Alexandria within the Ptolemaic court. Nonetheless,