Ahmed ibn Yusuf
Encyclopedia
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 .
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.
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. 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
.
Arab
Arab people, also known as Arabs , are a panethnicity primarily living in the Arab world, which is located in Western Asia and North Africa. They are identified as such on one or more of genealogical, linguistic, or cultural grounds, with tribal affiliations, and intra-tribal relationships playing...
mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, like his father Yusuf ibn Ibrahim .
Life
Ahmad ibn Yusuf was born in BaghdadBaghdad
Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...
and moved with his father to Damascus
Damascus
Damascus , commonly known in Syria as Al Sham , and as the City of Jasmine , is the capital and the second largest city of Syria after Aleppo, both are part of the country's 14 governorates. In addition to being one of the oldest continuously inhabited cities in the world, Damascus is a major...
in 839. He later moved to Cairo
Cairo
Cairo , is the capital of Egypt and the largest city in the Arab world and Africa, and the 16th largest metropolitan area in the world. Nicknamed "The City of a Thousand Minarets" for its preponderance of Islamic architecture, Cairo has long been a centre of the region's political and cultural life...
, 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
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
, Astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
and Medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, produced astronomical tables and was a member of a group of scholars. He achieved an important role in Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, which was caused by Egypt's relative independence from the Abbasid Caliph.
Work
For some of the work attributed to Ahmad, it is not exactly clear whether he wrote his, whether his father wrote it or whether they wrote it together. It is clear, however, that he worked on a book on ratioRatio
In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...
and proportion
Proportionality (mathematics)
In mathematics, two variable quantities are proportional if one of them is always the product of the other and a constant quantity, called the coefficient of proportionality or proportionality constant. In other words, are proportional if the ratio \tfrac yx is constant. We also say that one...
. This was translated to Latin by Gherard of Cremona and was a commentary of Euclid
Euclid
Euclid , fl. 300 BC, also known as Euclid of Alexandria, was a Greek mathematician, often referred to as the "Father of Geometry". He was active in Alexandria during the reign of Ptolemy I...
's Elements. This book influenced early European mathematicians such as Fibonacci. Further, in On similar arcs, he commented on Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
's Karpos (or Centiloquium
Centiloquium
The Centiloquium , also called Ptolemy's Centiloquium, is a collection of one hundred aphorisms about astrology and astrological rules...
); many scholars believe that ibn Yusuf was in fact the true author of that work. He also wrote a book on the astrolabe
Astrolabe
An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...
. 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
Thomas Bradwardine was an English scholar, scientist, courtier and, very briefly, Archbishop of Canterbury. As a celebrated scholastic philosopher and doctor of theology, he is often called Doctor Profundus, .-Life:He was born either at Hartfield in Sussex or at Chichester, where his family were...
, Jordanus de Nemore and Luca Pacioli
Luca Pacioli
Fra Luca Bartolomeo de Pacioli was an Italian mathematician, Franciscan friar, collaborator with Leonardo da Vinci, and seminal contributor to the field now known as accounting...
.