Habash al-Hasib al-Marwazi
- Habash al-Hasib al-Marwazi
Ahmad ibn 'Abdallah Habash al-Hasib al-Marwazi ( _ar. أحمد بن عبدالله المروزي حبش الحاسب) was a Persian astronomer and mathematician from Merv in Khorasan, Persia.
He flourished in Baghdad, and died a centenarian between 864 and 874. He worked under the Abbasid caliphs al-Ma'mun and al-Mu'tasim.
He made observations from 825 to 835, and compiled three astronomical tables: the first were still in the Hindu manner; the second, called the 'tested" tables, were the most important; they are likely identical with the "Ma'munic" or "Arabic" tables and may be a collective work of al-Ma'mun's astronomers; the third, called tables of the Shah, were smaller.
Apropos of the solar eclipse of 829, Habash gives us the first instance of a determination of time by an altitude (in this case, of the sun); a method which was generally adopted by Muslim astronomers.
He also seems to have introduced the notion of "shadow," umbra (versa), equivalent to our tangent in trigonometry, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced the cotangent, and produced the first tables of for it.[cite web|title=trigonometry|url=http://www.britannica.com/EBchecked/topic/605281/trigonometry|publisher="Encyclopædia Britannica"|accessdate=2008-07-21] ]References
ee also
*List of Iranian scientists
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