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(; (ペルシア語:ابوسهل بیژن کوهی) ''Abusahl Bijan-e Koohi'') was a Persian〔(al-Quhi, Abu Sahl Wayjan ibn Rustam (c. 940-c. 1000) )〕 mathematician, physicist and astronomer. He was from Kuh (or Quh), an area in Tabaristan, Amol, and flourished in Baghdad in the 10th century. He is considered one of the greatest Muslim geometers, with many mathematical and astronomical writings ascribed to him. He was the leader of the astronomers working in 988 AD at the observatory built by the Buwayhid Sharaf al-Dawla in Badhdad. He wrote a treatise on the astrolabe in which he solves a number of difficult geometric problems. In mathematics he devoted his attention to those Archimedean and Apollonian problems leading to equations higher than the second degree. He solved some of them and discussed the conditions of solvability. For example, he was able to solve the problem of inscribing a regular pentagon into a square, resulting in an equation of fourth degree.〔Hogendijk: "al-Kuhi's construction of an equilateral pentagon in a given square", ''Zeitschrift für Gesch. Arab.-Islam. Wiss.'', Volume 1, 1984, pp. 100-144; correction and addendum Volume 4, 1986/87, p.267〕 He also wrote a treatise on the "perfect compass", a compass with one leg of variable length that allows to draw any conic section: straight lines, circles, ellipses, parabolas and hyperbolas. It is likely that al-Quhi invented the device. Like Aristotle, al-Quhi proposed that the heaviness of bodies vary with their distance from the center of the Earth.〔Mohammed Abattouy (2002), "The Arabic Science of weights: A Report on an Ongoing Research Project", ''The Bulletin of the Royal Institute for Inter-Faith Studies'' 4, p. 109-130〕 The correspondence between al-Quhi and Abu Ishaq al-Sabi, a high civil servant interested in mathematics, has been preserved.〔Berggren: "The correspondence of Abu Sahl al-Kuhi and Abu Ishaq al-Sabi: a translation with commentaries", ''J. Hist. Arabic Sci.'', volume 7, 1983, pp. 39-124.〕 ==Notes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Abū Sahl al-Qūhī」の詳細全文を読む スポンサード リンク
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