Abu Ja'far Ahmad ibn Yusuf ibn Ibrahim ibn Tammam al-Siddiq Al-Baghdadi (; 835–912), known in the West by his

Latinized name Latinisation (or Latinization) of names, also known as onomastic Latinisation (or onomastic Latinization), is the practice of rendering a ''non''-Latin name in a modern Latin style. It is commonly found with historical proper names, including p ...

Hametus, was a

Muslim Muslims () are people who adhere to Islam, a Monotheism, monotheistic religion belonging to the Abrahamic religions, Abrahamic tradition. They consider the Quran, the foundational religious text of Islam, to be the verbatim word of the God ...

Arab Arabs (, , ; , , ) are an ethnic group mainly inhabiting the Arab world in West Asia and North Africa. A significant Arab diaspora is present in various parts of the world. Arabs have been in the Fertile Crescent for thousands of years ...

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

, like his father Yusuf ibn Ibrahim ().

Life

Ahmad ibn Yusuf was born in

Baghdad Baghdad ( or ; , ) is the capital and List of largest cities of Iraq, largest city of Iraq, located along the Tigris in the central part of the country. With a population exceeding 7 million, it ranks among the List of largest cities in the A ...

and moved with his father to

Damascus Damascus ( , ; ) is the capital and List of largest cities in the Levant region by population, largest city of Syria. It is the oldest capital in the world and, according to some, the fourth Holiest sites in Islam, holiest city in Islam. Kno ...

in 839. He later moved to

Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...

, 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 Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

and

Medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

, produced astronomical tables and was a member of a group of scholars. He achieved an important role in

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

, which was caused by Egypt's relative independence from the

Abbasid Caliph The Abbasid caliphs were the holders of the Islamic title of caliph who were members of the Abbasid dynasty, a branch of the Quraysh tribe descended from the uncle of the Islamic prophet Muhammad, Al-Abbas ibn Abd al-Muttalib. The family came ...

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 In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...

and proportion. This was translated to Latin by Gherard of Cremona and was a commentary of

Euclid Euclid (; ; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the '' Elements'' treatise, which established the foundations of geometry that largely domina ...

's ''Elements''. This book influenced early European mathematicians such as

Fibonacci Leonardo Bonacci ( – ), commonly known as Fibonacci, was an Italians, Italian mathematician from the Republic of Pisa, considered to be "the most talented Western mathematician of the Middle Ages". The name he is commonly called, ''Fibonacci ...

. Further, in ''On similar arcs'', he commented on

Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...

's ''Karpos'' (or '' Centiloquium''); many scholars believe that ibn Yusuf was in fact the true author of that work.Richard Lemay, Origin and success of the ''Kitab Thamara'' of Abu Ja'far Ahmad ibn Yusuf, in ''Proceedings of the 1st International Symposium for the History of Arabic Science, University of Aleppo (1976)'', Aleppo 1978 He also wrote a book on the

astrolabe An astrolabe (; ; ) is an astronomy, astronomical list of astronomical instruments, instrument dating to ancient times. It serves as a star chart and Model#Physical model, physical model of the visible celestial sphere, half-dome of the sky. It ...

. 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 Thomas Bradwardine (c. 1300 – 26 August 1349) was an English cleric, scholar, mathematician, physicist, courtier and, very briefly, Archbishop of Canterbury. As a celebrated scholastic philosopher and doctor of theology, he is often ca ...

Jordanus de Nemore Jordanus de Nemore (fl. 13th century), also known as Jordanus Nemorarius and Giordano of Nemi, was a thirteenth-century European mathematician and scientist. The literal translation of Jordanus de Nemore (Giordano of Nemi) would indicate that he ...

and

Luca Pacioli Luca Bartolomeo de Pacioli, O.F.M. (sometimes ''Paccioli'' or ''Paciolo''; 1447 – 19 June 1517) was an Italian mathematician, Franciscan friar, collaborator with Leonardo da Vinci, and an early contributor to the field now known as account ...

Notes

* * H. L. L. Busard and P. S. van Koningsveld, ''Der "Liber de arcubus similibus" des Ahmad ibn Jusuf'',

Annals of science ''Annals of Science'' is a peer-reviewed academic journal covering the history of science and technology. It is published by Taylor & Francis and was established in 1936. The founding editor-in-chief was the Canadian historian of science Harcourt ...

30 (1973), 381–406. * M Steinschneider, Yusuf ben Ibrahim und Ahmad ibn Yusuf, Bibliotheca mathematic (1888), 49–117.

External links

* * {{DEFAULTSORT:Ahmad ibn Yusuf Astronomers from the Abbasid Caliphate People from Baghdad 9th-century mathematicians 10th-century mathematicians 835 births 912 deaths 9th-century Arab people 10th-century Arab people Mathematicians from the Abbasid Caliphate 10th-century astronomers 10th-century people from the Abbasid Caliphate

Life

Work

See also

Notes

External links