Habash al-Hasib | |
|---|---|
حبش الحاسب | |
| Born | Ahmad ibn ‘Abdallah al-Marwazi |
| Died | Between 864–874 (aged 100) Possibly inAbbasid Samarra,Abbasid Caliphate |
| Known for | tangent and cotangent,Kepler's equation |
| Children | Abu Ja'far ibn Habash |
| Scientific career | |
| Fields | Astronomy |
Ahmad ibn 'Abdallah al-Marwazi,[1][2] known asHabash al-Hasib (Persian:حبش الحاسب,lit. 'Abyssinian calculator',[1][2][3] diedc. 869[4]) was aPersian[5][2]astronomer,[6]geographer, andmathematician fromMerv inKhorasan, who discovered thetrigonometric ratiostangent, andcotangent.[7]Al-Biruni who cited Habash in his work, expanded his astronomical tables.[3]
Habash al-Hasib flourished inBaghdad, and died a centenarian some time between 864 and 874[2][3][8] possibly inAbbasid Samarra.[4] The title "Habash" (Abbyssian) may refer to dark skin color.[3] He worked under twoAbbasid caliphs,al-Ma'mun andal-Mu'tasim.[3]
Habash al-Hasib developed a trigonometric algorithm to solve problems related toparallax, which was later rediscovered byJohannes Kepler in 1609 and it is now known asKepler's equation.[9][10]
Habash is the father of the astronomerAbu Ja'far ibn Habash.[3]
Habash Hasib madeastronomical observations from 825 to 835, and compiled threezijes (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 thesolar 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.
In 860, he seems to have introduced the notion of "shadow", umbra (versa), equivalent to ourtangent intrigonometry, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced thecotangent, and produced the first tables of for it.[11][12]
Habash al-Hasib conducted various observations at theAl-Shammisiyyah observatory inBaghdad and estimated a number of geographic and astronomical values. He compiled his results inThe Book of Bodies and Distances (Kitāb al-ajrām wa-l-ab 'ād),[8] in which some of his results included the following:[13]
{{cite book}}:ISBN / Date incompatibility (help){{cite web}}: CS1 maint: archived copy as title (link)The first table of tangents and cotangents was constructed around 860 by Ḥabash al-Ḥāsib ("the Calculator"), who wrote on astronomy and astronomical instruments.
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