Abd al-Qahir Al-Baghdadi

Full name: 
Abū Mansūr Abd al-Qāhir Ibn Tāhir Ibn Muhammad Ibn ‘Abdallāh al-Tamīmī al-Baghdādī
Arabic name: 
أبو منصور عبد القاهر بن طاهر بن محمد بن عبد الله التميمي البغدادي
Latin name: 
Machometus Bagdedinus
Date of birth: 
Date of death: 

He was an Arab mathematician (c. 980–1037) from Baghdad who is best known for his treatise al-Takmila fi'l-Hisab. It contains results in number theory, and comments on works by al-Khwarizmi which are now lost.

To give just one example of his works translated into Latin, we quote his work on the divisions of superficies: De superficierum divisionibus liber Machometo Bagdedino ascriptis nunc primum Ioannis Dee londinensis, et Federici Commandini urbinatis opera in lucem editus. Federici Commandini de eadem re libellus, prinyed in Pesaro in 1570. The influence of this book lasted until the 17th century, when the leading Jesuit mathematician Christoph Clavius, from the famous Collegio Romano, made use of it in his Practical Geometry.

Among his writings, al-Takmila fi'l-Hisab, is a work of major importance in the history of mathematics in which al-Baghdadi considers different systems of arithmetic. These systems derive from counting on the fingers, the sexagesimal system, and the arithmetic of the Indian numerals and fractions. He also considers the arithmetic of irrational numbers and business arithmetic. He further stresses the benefits of each of the systems but seems to favour the Indian numerals.

See on the mathematical contribution of al-Baghdadi his scientific biography in MacTutor History of Mathematics.