Kushyar ibn Labban
Encyclopedia
Abul-Hasan Kūshyār ibn Labbān ibn Bashahri Gilani (971–1029), also known as Kūshyār Gīlānī , was a Persian 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....

, geographer
Geographer
A geographer is a scholar whose area of study is geography, the study of Earth's natural environment and human society.Although geographers are historically known as people who make maps, map making is actually the field of study of cartography, a subset of geography...

, and astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

 from Gilan, south of the Caspian Sea
Caspian Sea
The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...

, Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

.

His main work was probably done about the beginning of the eleventh century, and seems to have taken an important part in the elaboration of trigonometry
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...

. For example, he continued the investigations of Abul Wáfa
Abul Wáfa
Abū al-Wafāʾ, Muḥammad ibn Muḥammad ibn Yaḥyā ibn Ismāʿīl ibn al-ʿAbbās al-Būzjānī was a Persian mathematician and astronomer who worked in Baghdad...

, and devoted much space to this in his zij
Zij
Zīj is the generic name applied to Islamic astronomical books that tabulate parameters used for astronomical calculations of the positions of the Sun, Moon, stars, and planets. The name is derived from the Middle Persian term zih or zīg, meaning cord...

 (or collection of tables) az-Zīj al-Jamī wal-Baligh ("the comprehensive and mature tables"), which incorporated the improved values of the planetary apogees observed by al-Battani
Al-Battani
Abū ʿAbd Allāh Muḥammad ibn Jābir ibn Sinān al-Raqqī al-Ḥarrānī al-Ṣābiʾ al-Battānī was a Muslim astronomer, astrologer, and mathematician...

. The tables were translated into Persian before the end of the century. He wrote also an astrological introduction and an arithmetic treatise Kitab fi usul hisab al-hind (Principles of Hindu Reckoning
Principles of Hindu Reckoning
Principles of Hindu Reckoning is a mathematics book written by 10th–11th-century Persian mathematician Kushyar ibn Labban...

, extant in Arabic and Hebrew).

He was the teacher of Ahmad Nasawi. He is thought to have died in Baghdad
Baghdad
Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...

.

Sources

  • H. Suter: Mathematiker und Astronomen der Araber (83, 235, 1900; 168, 1902).
  • M Levey and M Petruck (trs.), Kushyar ibn Labban, Principles of Hindu reckoning (Madison, 1965).

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