What is "al-nayrizi"

Abū’l-‘Abbās al-Faḍl ibn Ḥātim al-Nairīzī (, , 865–922) was a 9th-10th century Persian mathematician and astronomer from Nayriz, Fars Province, Iran.

He flourished under al-Mu'tadid, Caliph from 892 to 902, and compiled astronomical tables, writing a book for al-Mu'tadid on atmospheric phenomena.

Nayrizi wrote commentaries on Ptolemy and Euclid. The latter were translated by Gerard of Cremona. Nairizi used the so-called umbra (versa), the equivalent to the tangent, as a genuine trigonometric line (but he was anticipated in this by al-Marwazi).

He wrote a treatise on the spherical astrolabe, which is very elaborate and seems to be the best Persian work on the subject. It is divided into four books:

1. Historical and critical introduction.
2. Description of the spherical astrolabe; its superiority over plane astrolabes and all other astronomical instruments.
3. Applications.
4. Applications.

He gave a proof of the Pythagorean theorem using the Pythagorean tiling.

Ibn al-Nadim mentions Nayrizi as a distinguished astronomer with eight works by him listed in his book al-Fihrist.