A brilliant Andalusian mathematician (b. 989, Cordova, Al-Andalus – d. 1079, Jaen, Al-Andalus). He wrote important commentaries on Euclid's Elements and he wrote the first treatise on spherical trigonometry. Little is known about his life. Some of his works translated into Latin were ascribed to Alhazen, the Latinised name of Ibn al-Haytham, such as the famous Liber de crepusculis (Treatise on twilight), in which height of the atmospheric moisture responsible for the refraction of the sun's rays is calculated. This work, generally ascribed to Alhazen, is the work of al-Jayyani.
Among his known works, Tabulae Jahen cum regulis suis is a set of astronomical tables for Jaen, an Andalusian city.