Theon of Alexandria
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Theon (c. 335 - c. 405 AD) was a scholar and the last director of the Library of Alexandria in the Museion, until it was closed by the patriarch Theophilus on order of the emperor Theodosius I in 391 AD. Theon was the father of the mathematician and "pagan martyr" Hypatia.
Theon's most durable achievement may be his edition of Euclid's Elements, published around 364 and authoritative into the 19th century. The bulk of Theon's work, however, consisted of commentaries on important works by his hellenistic predecessors. These included a "conferences" (Synousiai) on Euclid, and commentaries (Exegeseis) on the Handy Tables and Almagest of Ptolemy, and on the technical poet Aratus.
In one of the commentaries on the Handy Tables, he is the first author to describe the theory of trepidation of the equinoxes, as an alternative to precession. Theon described but did not endorse this theory.
[edit] References
G. J. Toomer, "Theon of Alexandria," in Dictionary of Scientific Biography 13:321-325.