Al-Jayyani, the mathematician, is described as a judge and a jurist in one of his treatises. The only possible problem to the identification is that al-Jayyani wrote a treatise on the total solar eclipse which occurred in Jaén on 1 July 1079. The identification means that he was over ninety years old when he wrote this treatise which, although certainly not impossible, casts a slight doubt.
The only other facts known about al-Jayyani's life are that he lived in Cairo from 1012 to 1017 and that he must have undertaken most of his work in Jaén, the city at the centre of the Moorish principality of Jayyan. This cannot only be deduced from his name "al-Jayyani" which means "from Jaén", but also from the fact that the astronomical tables that he produced were for the longitude of Jaén. Certainly he observed the solar eclipse in Jaén in 1079.
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