The famous Iranian-Islamic mathematician and astronomer, Abdul-Jalil as-Sijzi
Compiled By: Syed Ali Shahbaz
On 6th of the Islamic month of Jamadi al-Awwal in 414 AH the famous Iranian-Islamic mathematician and astronomer, Abu Sa'eed Ahmad ibn Mohammad ibn Abdul-Jalil as-Sijzi, passed away at the age of 77. He was from Sistan which in those days was also called Sijistan, hence his epithet as-Sijzi.
He had a deep knowledge of literature which he used to his advantage. He dedicated his astronomical work to Azod od-Dowla the ruler of the Buwayhid kingdom of Iran and Iraq. He also dedicated another of his works to the ruler of Balkh in Greater Khorasan. He also worked in Shiraz making astronomical observations from 969 to 970. He also did a lot of geometry work.
Abu Rayhan Birouni wrote that Sijzi believed in a heliocentric system in which the Earth was moving and that he invented an astrolabe called the "Zuraqi" based on this idea. As a mathematician, Sijzi made a special study of the intersections of conic sections and circles. He replaced the old kinematical trisection of an angle by a purely geometric solution (intersection of a circle and an equilateral hyperbola.)