Quhi

Abu Sahl Wayjan ibn Rustam al Quhi

Born: about 940 in Tabaristan (now Mazanderan), Persia (now Iran)
Died: about 1000

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Al-Quhi worked in Baghdad. In 969 and 970 he made observations of the winter and summer solstices in Shiraz. In 988 he organised the building of an observatory to study the planets. After building was complete al-Quhi became the director and some accurate observations were made but the observatory ceased work in 989.

Al-Quhi worked chiefly in geometry and considered problems leading to quadratic or cubic equations. Nasir al-Din al-Tusi wrote:-

To construct a sphere segment equal in volume to a given sphere segment and equal in area to a second sphere segment - a problem similar to but more difficult than related problems solved by Archimedes - Al-Quhi constructed the two unknown lengths by intersecting an equilateral hyperbola with a parabola and rigorously discussed the conditions under which the problem is soluble.

Al-Quhi also described a conic compass, a compass with one leg of variable length, for drawing conic sections.

References:

  1. Dictionary of Scientific Biography
  2. A P Youschkevitch, Geschichte der Mathematik im Mittelalter (Basel, 1964), 258-259, 292. 
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JOC/EFR February 1996