Ahmad ibn Yusuf

Abu Ja'far Ahmad ibn Yusuf ibn Ibrahim ibn Tammam al-Siddiq Al-Baghdadi (835–912), known in the West by his Latinized name Hametus, was an Arab mathematician, like his father Yusuf ibn Ibrahim (Arabic: يوسف بن ابراهيم الصدَيق البغدادي ‎‎).

Life

Ahmad ibn Yusuf was born in Baghdad and moved with his father to Damascus in 839. He later moved to Cairo, but the exact date is unknown: since he was also known as al-Misri, which means the Egyptian, this probably happened at an early age. Eventually, he also died in Cairo. He probably grew up in a strongly intellectual environment: his father worked on Mathematics, Astronomy and Medicine, produced astronomical tables and was a member of a group of scholars. He achieved an important role in Egypt, which was caused by Egypt's relative independence from the Abbasid Caliph.

Work

In some of the works attributed to Ahmad, it is not clear if the text came from him, his father, or whether they wrote together. It is clear, however, that he worked on a book on ratio and proportion. This was translated to Latin by Gherard of Cremona and was a commentary of Euclid's Elements. This book influenced early European mathematicians such as Fibonacci. Further, in On similar arcs, he commented on Ptolemy's Karpos (or Centiloquium); many scholars believe that ibn Yusuf was in fact the true author of that work.^[1] He also wrote a book on the astrolabe. He invented methods to solve tax problems that were later presented in Fibonacci's Liber Abaci. He was also quoted by mathematicians such as Thomas Bradwardine, Jordanus de Nemore and Luca Pacioli.

See also

• List of Arab scientists and scholars

Notes

• M Steinschneider, Yusuf ben Ibrahim und Ahmad ibn Yusuf, Bibliotheca mathematic (1888), 49–117.
• Schrader, Dorothy (1970). "Aḥmad Ibn Yūsef". Dictionary of Scientific Biography. 1. New York: Charles Scribner's Sons. pp. 82–83. ISBN 0-684-10114-9. 
• H. L. L. Busard and P. S. van Koningsveld, Der "Liber de arcubus similibus" des Ahmad ibn Jusuf, Annals of science 30 (1973), 381–406.
• M Steinschneider, Yusuf ben Ibrahim und Ahmad ibn Yusuf, Bibliotheca mathematic (1888), 49–117.

External links

• O'Connor, John J.; Robertson, Edmund F., "Ahmad ibn Yusuf", MacTutor History of Mathematics archive, University of St Andrews .
• Schrader, Dorothy V. (2008) [1970–80]. "Aḥmad Ibn Yūsuf". Complete Dictionary of Scientific Biography. Encyclopedia.com. 

Mathematics in medieval Islam
Mathematicians (Works)	9th century 'Abd al-Hamīd ibn Turk Sind ibn Ali Al-Abbās ibn Said al-Jawharī Al-Ḥajjāj ibn Yūsuf ibn Maṭar Al-Kindi De Gradibus Al-Mahani Banū Mūsā Hunayn ibn Ishaq al-Khwārizmī The Compendious Book on Calculation by Completion and Balancing ibn Qurra Na'im ibn Musa Sahl ibn Bishr Habash al-Hasib al-Marwazi Abu Said Gorgani 10th century Abd al-Rahman al-Sufi Book of Fixed Stars Abu al-Wafa' Buzjani Abū Ja'far al-Khāzin Abū Kāmil Shujāʿ ibn Aslam Abu'l-Hasan al-Uqlidisi Abu-Mahmud Khojandi Ahmad ibn Yusuf Al-Nayrizi Al-Saghani Brethren of Purity Ibn Sahl Ibn Yunus Ibrahim ibn Sinan Al-Battani Sinan ibn Thabit Al-Isfahani Nazif ibn Yumn Abū Sahl al-Qūhī Abu al-Jud 11th century Abū Ishāq Ibrāhīm al-Zarqālī Abu Nasr Mansur Al-Biruni Ibn al-Haytham / Alhazen Book of Optics Ibn Muʿādh al-Jayyānī Al-Karaji Al-Sijzi Alī ibn Ahmad al-Nasawī Avicenna The Book of Healing Abu Mansur al-Baghdadi Kushyar Gilani Yusuf al-Mu'taman ibn Hud Abu Mansur al-Baghdadi Al-Isfizari 12th century Al-Khazini Al-Samawal al-Maghribi Omar Khayyam Jabir ibn Aflah Abu Bakr al-Hassar 13th century Muhyi al-Dīn al-Maghribī Nasir al-Din al-Tusi Zij-i Ilkhani Shams al-Dīn al-Samarqandī Sharaf al-Dīn al-Ṭūsī Ibn al‐Ha'im al‐Ishbili Ibn Abi al-Shukr 14th century Yaʿīsh ibn Ibrāhīm al-Umawī Ibn al-Banna' al-Marrakushi Ibn al-Shatir Kamāl al-Dīn al-Fārisī Al-Khalili Qutb al-Din al-Shirazi Ahmad al-Qalqashandi 15th century Abū al-Ḥasan ibn ʿAlī al-Qalaṣādī Ali Qushji Jamshīd al-Kāshī Qāḍī Zāda al-Rūmī Ulugh Beg Ibn al-Majdi 16th century Al-Birjandi Muhammad Baqir Yazdi Taqi ad-Din Ibn Hamza al-Maghribi Ibn Ghazi al-Miknasi
Other treatises	Almanac Encyclopedia of the Brethren of Purity Toledan Tables Tabula Rogeriana Zij Zij-i Sultani
Concepts	Alhazen's problem Islamic geometric patterns
Centers	Al-Azhar University Al-Mustansiriya University House of Knowledge House of Wisdom Constantinople observatory of Taqi al-Din Madrasa Maktab Maragheh observatory University of Al Quaraouiyine
Influences	Babylonian mathematics Greek mathematics Indian mathematics
Influenced	Byzantine mathematics European mathematics Indian mathematics