Arabic name: Ahmed Bin Yusuf Bin Ibrahim Al-Misri Bin Ad-Daya AHMED Bin Yusuf was born in Baghdad and moved to Damascus in 839, then to Cairo, where he died in 912 CE. He was a mathematician, like his father Yusuf Bin Ibrahim. Among his works that brought him fame and influence is his “Treatise on ratio and proportionality”. This was translated into Latin by Gherard of Cremona. It influenced early European mathematicians such as Fibonacci. Further, in “On similar arcs”, he commented on Ptolemy's Centiloquium. He also wrote a book on the astrolabe, a predecessor of the octant and the sextant. He invented methods to solve tax problems in Liber Abaci. He was also quoted by mathematicians such as Thomas Bradwardine, Jordanus Nemorarius and Luca Pacioli. His book “On similar arcs” influenced European mathematicians, as Ahmed Bin Yusuf proves that similar arcs of circles can be equal and not equal. The proof, like that on ratio and proportion, is based on Euclid.
