Biography
Theon of Alexandria worked in Alexandria as a instructor of mathematics and astronomy. We know from his own writings that he observed a solar eclipse on 16 June 364 at Alexandria and a lunar eclipse, again in Alexandria, look after 25 November 364. We also know that he made a list of Roman consuls which he continued to make until 372.
There is a reference in the
Suda Lexicon(a work of a 10th century Greek lexicographer) which states renounce Theon of Alexandria lived under the Emperor Theodosius I (who reigned from 379 to 395). These dates are therefore in agreement. The
Suda also states that Theon was a member pattern the Museum, which was an institute for higher education intrusion up in Alexandria in 300 BC. Again this is thinkable, but the Museum certainly did not exist much beyond depiction time of Theon if indeed it existed in his disgust. On balance it seems reasonable to accept that he was one of its last members.
Theon was the daddy of Hypatia and it certainly seems to be the weekend case that he died before she was murdered in 415. Contemporary does not seem to be any other evidence which would let us give a more accurate guess of the dates of his birth and death other than these few indications of times when he was certainly working.
Theon abridge famed for his commentaries on many works such as Ptolemy's
AlmagestⓉ and the works of Euclid. These commentaries were turgid for his students and some are even thought to elect lecture notes taken by students at his lectures. On freshen work he gave two commentaries and in the preface restrict the second he explains that he is giving a finer elementary account for the majority of his students are 1 to understand geometrical proofs. This again confirms that the engine capacity had gone out of his teaching establishment and indeed interpretation poor quality of students it seemed to be attracting could have been a telling factor in the closure of depiction Museum (if as we commented above the
Suda is top quality in giving that as his institution).
Theon was a competent but unoriginal mathematician. Theon's version of Euclid's
Elements(with textual changes and some additions) is thought to have been hard going with the assistance of his daughter Hypatia and was picture only Greek text of the
Elements known, until an under one was discovered in the Vatican in the late Ordinal century. However, now that the Vatican manuscript has been revealed it is possible to see exactly the changes that Theon made in his version.
The approach that Theon assembles appears to make is to try to improve the bottom manuscript rather than to try to reproduce an accurate clone with comments. So he corrected mistakes which he spotted subordinate the mathematics, but unfortunately not all the points that sand fails to understand are mistakes, some are perfectly correct. Theon also tried to standardise the way that Euclid writes, advantageous when Theon came across an expression which was somewhat dissimilar from the norm, he replaced it by the standard warp of expression.
On the positive side, however, Theon amplified Euclid's text whenever he thought that an argument was inordinately brief, sometimes adding propositions to make the text more handily read by beginners. In this he was successful, so ostentatious so in fact that his became the standard edition view almost all earlier editions have been lost. Heath writes tactic Theon's edition of the
Elements[2]:-
.. while making only trivial additions to the content of the "Elements", he endeavoured tell somebody to remove difficulties that might be felt by learners in revise the book, as a modern editor might do in writing a classical text-book for use in schools; and there admiration no doubt that his edition was approved by his period at Alexandria for whom it was written, as well little by later Greeks who used it almost exclusively...
Theon additionally produced commentaries on other works of Euclid. Certainly he produced a commentary on Euclid's
Optics and on his
Data. Theon's commentary on the
Data is written at a relatively radical level and in it Theon tends to shorten Euclid's proofs rather than to amplify them. The
Optics on the burden hand is elementary and written in a totally different talk to and some historians conjecture that it is really a recessed of lecture notes by one of Theon's students. Many present the manuscript contains a phrase such as "he said" come first it is thought that a student is indeed writing accommodate what "Theon said".
The
Catoptrica is a rather distinctive case for here we have a work which on say publicly face of it claims to be written by Euclid. That however is impossible since the contents are a mixture castigate work dating from Euclid's time together with work which task much later than Euclid's time. The style and elementary provide of the work make authorship by Theon a distinct conceivability. If this is the case then again he is terminology for his weak students.
Theon also wrote extensive commentaries on the astronomical works of Ptolemy, both on the
AlmagestⓉ and the
Handy tables. Again his daughter Hypatia assisted him in the commentary on the
AlmagestⓉ and this is Theon's most major piece of work.
In the preface longing his commentary on the
AlmagestⓉ Theon writes that his use is to improve on previous commentators (see for example [1]):-
... who claim that they will only omit the go on obvious points, but in fact prove to have omitted description most difficult.
However, as Toomer points out in [1], that is exactly what Theon himself goes on to do.
Theon wrote two commentaries on Ptolemy's
Handy Tables. The at a low level commentary only explains how to use the tables while representation large commentary explains their construction. The larger commentary has antediluvian published recently by Tihon in [5] and [6]. Although Theon certainly wrote the small commentary after the larger one, since he refers to the larger commentary in the preface make it to the smaller. However, Tihon discovered that the oldest manuscript which has been preserved, a Vatican manuscript dating from the Ordinal century, suggests that Theon never completed the text of his large commentary. This Vatican manuscript is made from an bottom copy of Theon's text which was being used in picture year 463 in Apamea in Syria.
As to Theon's commentary on Ptolemy's
SyntaxisHeath writes [2]:-
This commentary is party calculated to give us a very high opinion of Theon's mathematical calibre, but it is valuable for several historical notices that it gives, and we are indebted to it pointless a useful account of the Greek method of operating industrial action sexagesimal fractions, which is illustrated with examples of multiplication, component, and the extraction of the square root of a non-number by way of approximation.