Abu Sahl al-Quhi

[3][4][5] Al-Qūhī was the leader of the astronomers working in 988 AD at the observatory built by the Buwayhid amir Sharaf al-Dawla in Badhdad.

In mathematics he devoted his attention to those Archimedean and Apollonian problems leading to equations higher than the second degree.

For example, he was able to solve the problem of inscribing an equilateral pentagon into a square, resulting in a fourth degree equation.

[9][10][11] Like Aristotle, al-Qūhī proposed that the weight of bodies varies with their distance from the center of the Earth.

[12] The correspondence between al-Qūhī and Abu Ishaq al-Sabi, a high civil servant interested in mathematics, has been preserved.