Abu Sa'id Ahmed ibn Mohammed ibn Abd Jalil Sijzi (short for Sijistani) was a Persian

Persian people

The Persian people are part of the Iranian peoples who speak the modern Persian language and closely akin Iranian dialects and languages. The origin of the ethnic Iranian/Persian peoples are traced to the Ancient Iranian peoples, who were part of the ancient Indo-Iranians and themselves part of...

 astronomer

Islamic astronomy

Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...

 and mathematician

Islamic mathematics

In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...

 from Sistan

Sistan

Sīstān is a border region in eastern Iran , southwestern Afghanistan and northern tip of Southwestern Pakistan .-Etymology:...

, a region lying in the south-west of Afghanistan

Afghanistan

Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...

 and south-east of Iran

Iran

Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

.

Sijzi is thought to have been born around 945 CE, and lived through about 1020. His main scientific focus was astronomy. He had a deep knowledge of literature which he used to his advantage. He dedicated work to 'Adud al-Daula

'Adud al-Daula

Aḍud al-Dawla or Azod od-Dowleh Panah Khusraw was an emir of the Buyid dynasty in Iran and Iraq...

 and the prince of Balkh

Balkh

Balkh , was an ancient city and centre of Zoroastrianism in what is now northern Afghanistan. Today it is a small town in the province of Balkh, about 20 kilometers northwest of the provincial capital, Mazar-e Sharif, and some south of the Amu Darya. It was one of the major cities of Khorasan...

. He also worked in Shiraz making astronomical observations from 969 to 970. He also did a lot of geometry work.

Astronomy

Biruni wrote that Sijzi believed in a heliocentric system in which the Earth was moving and that he invented an astrolabe

Astrolabe

An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...

 called the "Zuraqi" based on this idea:

Mathematics

Sijzi was a mathematician who made a special study of the intersections of conic sections and circles. He replaced the old kinematical trisection of an angle by a purely geometric solution (intersection of a circle and an equilateral hyperbola.)

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