Sharaf al-Dīn al-Ṭūsī

Sharaf al -Din al- Muzaffar ibn Muhammad ibn al - Muzaffar al - Tusi (* 1135 in Tus, Khorasan province, Iran, † 1213 in Iran ) was a Persian mathematician and astronomer.

About his life little is known. 1154 he is in Damascus, where he taught mathematics and astronomy ( Euclid, Ptolemy ), and he also taught in Aleppo, where he gave both Jews and Muslims lessons. After that he went to Mosul, where he taught Kamal al -Din ibn Yunus, the teacher of Nasir ad-Din at- Tusi. Around the time of the conquest of Damascus by Saladin ( 1174 ), he returned to Iran. Towards the end of his life he taught in Baghdad, where in 1209 he wrote his book on algebra. It is obtained in a reworking of an unknown author.

In his Algebra he treats equations up to the third degree, taking applications in geometry has in mind ( Roshdi Rashed ). He used already implicitly derivative of a function (in this case of a polynomial in the determination of its maximum value ) in the discussion of the existence of solutions of individual cubic equations.

He also invented a rod astrolabe and published it.