Ahmad ibn Yusuf

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Ahmad ibn Yusuf ( Arabic أحمد بن يوسف البغدادي, DMG Aḥmad b. Yūsuf , Latinized Ametus, * before 839 in Baghdad ; † 912 or 913 in Cairo ) was a mathematician.

Ahmad ibn Yusuf came to Damascus in 839 with his father Yusuf ibn Ibrahim, a scholar who studied mathematics, astronomy and medicine, and later went to Cairo. Since he later bore the surname of the Egyptians (al-Misri), he lived there for a long time. He was employed as a secretary by the ruling family of the Tulun, who ruled from 868 to 905. He mentions a Huda ibn Ahmad ibn Tulun several times, possibly one of the sons of the ruler Ahmad ibn Tulun, who ruled until 884.

He wrote a commentary on Book 5 of the Elements of Euclid , which Gerhard of Cremona translated into Latin as Epistola de proportione et proportionalitate . Manuscripts are in the Paris National Library, the Laurenziana in Florence, the Austrian National Library and other libraries. In his classification of proportions he distinguished 18 cases. Besides Euclid's chapter on proportions and relationships, he also refers to the Almagest (Book 1, Chapter 13) by Claudius Ptolemy .

Ahmad ibn Yusuf influenced Fibonacci (who applied the work of Ahmad ibn Yusuf to tax problems) and his Liber Abaci , Thomas Bradwardine , Jordanus Nemorarius and Luca Pacioli . The Euclid commentator Campanus von Novara showed him to be a circular argument.

He penned a commentary on the Centiloquium , a collection of 100 aphorisms on astrology, incorrectly attributed to Claudius Ptolemy in the Middle Ages and known as the Book of Fruit (Kitab al-Tamara), Latin Liber Fructus , and by Plato of Tivoli and Johannes Hispalensis ins Latin was translated. It was still a textbook for medical students at the University of Bologna in the 15th century. According to Richard Lemay, Ahmad ibn Yusuf may be the author of the Centiloquium himself. Ahmad ibn Yusuf was sometimes confused with Ali ibn Ridwan (Haly), who wrote a commentary on the astrological main work Tetrabiblos by Claudius Ptolemy and also worked in Egypt.

He also wrote a book on similar bows and one on the astrolabe . All four works are in Arabic and, in addition to the book on the astrolabe, also in Latin translation.

literature

  • Moritz Steinschneider : Yusuf ben Ibrahim and Ahmad ibn Yusuf , Bibliotheca Mathematica, 1888, pp. 49–117.
  • Dorothy Schrader: Aḥmad Ibn Yūsef , in: Dictionary of Scientific Biography , Volume 1, pp. 82–83
  • HLL Busard, PS van Koningsveld: The "Liber de arcubus similibus" by Ahmad ibn Jusuf , Annals of Science, Volume 30, 1973, pp. 381-406.

Web links

Individual evidence

  1. ↑ Life data according to Dorothy Schrader, Dict. Sci. Biogr.
  2. ↑ After Dorothy Schrader, Dict. Sci. Biogr., At least 11 Latin manuscripts are known and several Arabic manuscripts, among others in Cairo and Algiers.
  3. Jump up ↑ Richard Lemay, Origin and Success of the Kitab Thamara of Abu Jafar ibn Yusuf ibn Ibrahim: From the Tenth to the Seventeenth Century in the World of Islam and the Latin West , in: Proceedings of the First International Symposium for the History of Arabic Science , April 5-12, 1976, Aleppo University, Vol. 2, pp. 91-107.
  4. ↑ Dorothy Schrader, article Ahmad ibn Yusuf in Dict. Sci. Biogr.
personal data
SURNAME Ahmad ibn Yusuf
ALTERNATIVE NAMES Hametus
BRIEF DESCRIPTION Arabic mathematician
DATE OF BIRTH before 839
PLACE OF BIRTH Baghdad
DATE OF DEATH 912 or 913
Place of death Cairo