Kushyar ibn Labban

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Kushyar ibn Labban (* in Gilan ; died in Baghdad ) was an Arab mathematician of the 10th and 11th centuries.

There are different spelling variants (Kusyan, Kushiyad, Koshar, Kusiar, Kossar) and name variants (al-Kiya, which means master, Jabah, Halebi).

He came from the Persian Gilan on the Caspian Sea. His father's name (Labban) means lion. According to the biographer al-Bayhaqi (died 1065), he died around 961, but the other biographical details rule this out as too early. Ibn al-Nadim does not mention him, but also lived in Baghdad and completed his work Fihrist by 995. It is usually assumed that he was active between 971 and 1029.

Little is known about Kushyar, except that he was the teacher of Ali ibn Ahmad al-Nasawi (fl. After 1029), the author of an arithmetic book. He mainly wrote astronomical works, tables and a book on astrolabe and astrology. Two astronomical treatises (Zij), al-Jami (manuscript in Leiden) and al-Baligh (in a Berlin manuscript, Berlin 5751) have survived. He did not make his own astronomical measurements, but took them from the school of Al-Battani . In his astronomical treatises there are also tables of trigonometric functions (as already started earlier by al-Battani and Abu l-Wafa ).

Kushyar is best known for a book on Indian numerals and arithmetic (Usul Hisab al-Hind), one of the oldest in the Arab world. It dates from around 1000. The main part deals with decimal numbers ( sexagesimal system only in tables). He knows zero but does not use a decimal point. Kushyar also gives methods of taking square roots and cube roots and uses the test of nine .

There is a 15th century Hebrew commentary on arithmetic by Anabi.

literature

  • AS Saidan: Kushyar ibn Labban ibn Bashahri, Abu 'L-Hasan, Al-Jili (fl. Approx. 1000), Dictionary of Scientific Biography , Volume 7, pp. 531-533
  • Martin Levey , M. Petruck (editor and translator): Kushyar ibn Labban, Principles of Hindu reckoning, Madison, 1965

Web links

personal data
SURNAME Kushyar ibn Labban
BRIEF DESCRIPTION Arabic mathematician
DATE OF BIRTH 10th century
PLACE OF BIRTH Gilan
DATE OF DEATH 11th century
Place of death Baghdad