Nasir al-Din al-Tusi

Nasir al-Din al-Tusi (1201-1274) was a Persian polymath active chiefly in the Ilkhanid Mongol court, working as an astronomer, mathematician, philosopher and theologian. Under the patronage of the Mongol ruler Hulagu Khan he founded and directed the Maragheh observatory in present day Iran, one of the best equipped observatories of its era, where he compiled the influential Zij-i Ilkhani astronomical tables. He devised the Tusi couple, a geometric technique for producing linear motion from combined circular motions that let him revise the Ptolemaic planetary models without violating uniform circular motion, and centuries later a strikingly similar construction appeared in Nicolaus Copernicus's own work, a resemblance historians still debate the transmission route for. He also wrote an influential treatise establishing trigonometry as a mathematical discipline independent of astronomy.