Abu Ja'far Ahmad ibn Yusuf ibn Ibrahim ibn Tammam al-Siddiq Al-Baghdadi ( ar, أبو جعفر أحمد بن يوسف بن ابراهيم بن تمام الصديق البغدادي; 835–912), known in the West by his

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

Hametus, was a

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

Arab The Arabs (singular: Arab; singular ar, عَرَبِيٌّ, DIN 31635: , , plural ar, عَرَب, DIN 31635: , Arabic pronunciation: ), also known as the Arab people, are an ethnic group mainly inhabiting the Arab world in Western Asia, ...

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, structure, space, models, and change. History On ...

, like his father Yusuf ibn Ibrahim ( ar, يوسف بن ابراهيم الصدَيق البغدادي ).

Life

Ahmad ibn Yusuf was born in

Baghdad Baghdad (; ar, بَغْدَاد , ) is the capital of Iraq and the second-largest city in the Arab world after Cairo. It is located on the Tigris near the ruins of the ancient city of Babylon and the Sassanid Persian capital of Ctesiphon ...

and moved with his father to

Damascus )), is an adjective which means "spacious". , motto = , image_flag = Flag of Damascus.svg , image_seal = Emblem of Damascus.svg , seal_type = Seal , map_caption = , ...

in 839. He later moved to

Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the capital of Egypt and its largest city, home to 10 million people. It is also part of the largest urban agglomeration in Africa, the Arab world and the Middle East: The Greater Cairo metr ...

, 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 an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

Astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...

and

Medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...

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

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a List of transcontinental countries, transcontinental country spanning the North Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via a land bridg ...

, 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 (; grc-gre, Εὐκλείδης; 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 ...

's ''Elements''. This book influenced early European mathematicians such as Fibonacci. Further, in ''On similar arcs'', he commented on

Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...

's ''Karpos'' (or ''

Centiloquium The ''Centiloquium'' (= "one hundred sayings"), also called ''Ptolemy's Centiloquium'', is a collection of one hundred aphorisms about astrology and astrological rules. It is first recorded at the start of the tenth century CE, when a commentary ...

''); 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 ( grc, ἀστρολάβος ; ar, ٱلأَسْطُرلاب ; persian, ستاره‌یاب ) is an ancient astronomical instrument that was a handheld model of the universe. Its various functions also make it an elaborate inclin ...

. 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 and

Luca Pacioli Fra Luca Bartolomeo de Pacioli (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 accounting ...

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 Arabs 10th-century Arabs Mathematicians from the Abbasid Caliphate 10th-century astronomers 10th-century people from the Abbasid Caliphate

Life

Work

See also

Notes

External links