Abul-Hasan Kūshyār ibn Labbān ibn Bashahri Daylami (971–1029), also known as Kūshyār Daylami (), was an

Iranian Iranian () may refer to: * Something of, from, or related to Iran ** Iranian diaspora, Iranians living outside Iran ** Iranian architecture, architecture of Iran and parts of the rest of West Asia ** Iranian cuisine, cooking traditions and practic ...

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, mathematical structure, structure, space, Mathematica ...

geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" a ...

, and

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

from

Daylam Daylam (), also known in the plural form Daylaman () (and variants such as Dailam, Deylam, and Deilam), was the name of a mountainous region of inland Gilan, Iran. It was so named for its inhabitants, known as the Daylamites. The Church of the Ea ...

, south of the

Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...

, Iran.

Career

Kūshyār Daylami's main work was probably done about the beginning of the 11th century, and seems to have taken an important part in the elaboration of

trigonometry Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The fiel ...

. He continued the investigations of the 10th century mathematician and astronomer Abul Wáfa, and devoted much space to this in his (book of astronomical tables) ("The Comprehensive and Mature Tables"), which incorporated the improved values of the planetary

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

s observed by

al-Battani Al-Battani (before 858929), archaically Latinized as Albategnius, was a Muslim astronomer, astrologer, geographer and mathematician, who lived and worked for most of his life at Raqqa, now in Syria. He is considered to be the greatest and mos ...

. The tables were translated into the

Persian language Persian ( ), also known by its endonym and exonym, endonym Farsi (, Fārsī ), is a Western Iranian languages, Western Iranian language belonging to the Iranian languages, Iranian branch of the Indo-Iranian languages, Indo-Iranian subdivision ...

before the end of the century. He wrote also an

astrological Astrology is a range of divinatory practices, recognized as pseudoscientific since the 18th century, that propose that information about human affairs and terrestrial events may be discerned by studying the apparent positions of celesti ...

introduction and an arithmetic

treatise A treatise is a Formality, formal and systematic written discourse on some subject concerned with investigating or exposing the main principles of the subject and its conclusions."mwod:treatise, Treatise." Merriam-Webster Online Dictionary. Acc ...

('' Principles of Hindu Reckoning'', that is extant in both

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

and

Hebrew Hebrew (; ''ʿÎbrit'') is a Northwest Semitic languages, Northwest Semitic language within the Afroasiatic languages, Afroasiatic language family. A regional dialect of the Canaanite languages, it was natively spoken by the Israelites and ...

), and was translated to English in 1963. Kūshyār Daylami's pupils included the Persian mathematician Al-Nasawi. Kūshyār Daylami is thought to have died in

Baghdad Baghdad ( or ; , ) is the capital and List of largest cities of Iraq, largest city of Iraq, located along the Tigris in the central part of the country. With a population exceeding 7 million, it ranks among the List of largest cities in the A ...

Career

References

Further reading