Jordanus Nemorarius (Germany, end of the 12th century 1225 - 1260) was a Mathématicien and scientist of origin probably Italy. It is also known under the names of Jordanus de Nemore and Giordano off Nemi . It had a great influence with the Moyen-âge and the Renaissance. There improves the theory of the tilted plan of Aristote, while remaining vague in its demonstration.