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Persian scholar Medieval era
Commemorated on an Iranian stamp upon the 700th anniversary of his death.
Name:	Nasir al-Din Tusi
Birth:	16th February, 1201 (11 Jamadi al-Ula, 597)
Death:	25th June, 1274 (18 Dhu'l-Hijjah 672)
School/tradition:	Shi'a
Main interests:	Theology Philosophy Mathematics Astronomy Medicine
Notable ideas:	Spherical trigonometry, Tusi-couple
Influences:	Ibn Sina Fakhr al-Din al-Razi
Influenced:	Qutb al-Din Shirazi Copernicus

For other uses, see Muhammad Nasir-al-din.

Nasir al-Din Muhammad ibn Muhammad ibn Hasan al-Tusi (Persian: خواجه نصیر طوسی‎ (1201–1274) was a Persian of Shi'a Twelver Islamic belief, born in Tus, Khorasan, Iran. He is known as a philosopher, mathematician, astronomer, theologian, physician, and a prolific writer, i.e., he was a polymath.

K. N. Toosi University of Technology in Iran is named after him.

Contents 1 Biography 2 Achievements 3 His works 4 Notes 5 See also 6 External links

Nasir al-Din Tusi was born in Tus in the year 1201 and began his studies at an early age. In Tus he studied Arabic, the Qur'an, Hadith, Shi'a Jurisprudence, logic, philosophy, mathematics, medicine and astronomy.^[1]

At a young age he moved to Nishapur to study Philosophy under Farid al-Din Damad and Mathematics under Muhammad Hasib.^[2]

As the armies of Genghis Khan swept his homeland, he fled to join the Ismailis and made his most important contributions in science during this time, while he was moving from one stronghold to another. He finally joined Hulagu's (Genghis Khan's son) ranks, after the invasion of the Alamut castle of the Hashshashin (Assassins) by Mongol forces.

The Mongol ruler, Hulagu Khan, built an observatory in Maragheh for Tusi. Tusi is considered the first of the Maragheh School of astronomers, who made significant contributions to the development of astronomy. Notable members of that school were Mu’ayyad al-Din al-’Urdi and Qutb al-Din al-Shirazi.

Tusi made very accurate tables of planetary movements as depicted in his book Zij-i ilkhani (the Ilkhanic Tables). This books contains astronomical tables for calculating the positions of the planets and the names of the stars. His planetary system was the most advanced of his period and was used extensively until the development of the heliocentric model in the time of Copernicus. Between Ptolemy and Copernicus, he is considered as one of the most eminent astronomer of his time.

He was perhaps the first to treat trigonometry as a separate mathematical discipline and in his Treatise on the Quadrilateral he was the first to list the six distinct cases of a right angled triangle in spherical trigonometry.

He invented the geometrical technique called a Tusi-couple for his planetary models, which generates linear motion from the sum of two circular motions. He also calculated the value of 51" for the annual precession of the equinoxes and contributed to construction and usage of some astronomical instruments including astrolabe. He gave the first extant exposition of the whole system of plane and spherical trigonometry.

A 60-km diameter lunar crater located on the southern hemisphere of the moon is named after him as "Nasireddin".

He also wrote extensively on biology and is one of the early pioneers of a kind of evolutionism in scientific thought. [1]

1. Al-Tadhkirah fi'ilm al-hay'ah (Memoir on the science of astronomy). Many commentaries were written about this work called Sharh al-Tadhkirah (A Commentary on al-Tadhkirah) among them were the commentary written by 'Abd al- 'Ali al-Birjandi and by Nazzam Nishapuri.
2. Akhlaq-i-Nasri a work on ethics
3. Tajrid-al-'Aqaid a major work on al-Kalam (Islamic Scholastic Philosophy)

1. ^ Dabashi, Hamid. "Khwajah Nasir al-Din al-Tusi: The philosopher/vizier and the intellectual climate of his times". Routledge History of World Philosophies. Vol I. History of Islamic Philosophy. Seyyed Hossein Nasr and Oliver Leaman (eds.) London: Routledge. 1996. p. 529
2. ^ Siddiqi, Bakhtyar Husain. "Nasir al-Din Tusi". A History of Islamic Philosophy. Vol 1. M. M. Sharif (ed.). Wiesbaden:: Otto Harrossowitz. 1963. p. 565

• List of Muslim scholars
• Islamic scholars
• List of Iranian scientists

• Biography by Islamic Philosophy Online
• Biography by The Internet Encyclopedia of Philosophy
• Biography by School of Mathematics and Statistics, University of St Andrews, Scotland
• History of Science Online: Islamic and Early Medieval Science, University of Oklahoma
• Islam Online.
• http://www.famousmuslims.com/NASIR%20AL-DIN%20AL-TUSI.htm
• http://www.britannica.com/eb/article-9073899