Ahmad ibn 'Abdallah Habash Hasib
Marwazi (766 - d. after 869
in Samarra, Iraq) was a Persian astronomer, geographer,
and mathematician from Merv in Khorasan who
for the first time described the trigonometric ratios: sine, cosine, tangent and cotangent.
He flourished in Baghdad, and died a centenarian after 869. He worked under the Abbasid caliphs al-Ma'mun and al-Mu'tasim.
Work
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.
In 830, he 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.
The Book of Bodies and Distances
Al-Hasib conducted various observations at the Al-Shammisiyyah
observatory in Baghdad and estimated a number of geographic and
astronomical values. He compiled his results in The Book of Bodies and
Distances, in which some of his results included the following:
Earth
·
Earth's circumference:
20,160 miles (32,444 km)
·
Earth's diameter:
6414.54 miles (10323.201 km)
·
Earth radius: 3207.275
miles (5161.609 km)
Moon
·
Moon's diameter: 1886.8
miles (3036.5 km)
·
Moon's circumference:
5927.025 miles (9538.622 km)
·
Radius of closest
distance of Moon: 215,208;9,9 (sexagesimal) miles
·
Half-circumference of
closest distance of Moon: 676,368;28,45,25,43 (sexagesimal) miles
·
Radius of furthest
distance of Moon: 205,800;8,45 (sexagesimal) miles
·
Diameter of furthest
distance of Moon: 411,600.216 miles (662,406.338 km)
·
Circumference of
furthest distance of Moon: 1,293,600.916 miles (2,081,848.873 km)
Sun
·
Sun's diameter:
35,280;1,30 miles (56,777.6966 km)
·
Sun's circumference:
110,880;4,43 miles (178,444.189 km)
·
Diameter of orbit of
Sun: 7,761,605.5 miles (12,491,093.2 km)
·
Circumference of orbit
of Sun: 24,392,571.38 miles (39,256,038 km)
·
One degree along
orbit of Sun: 67,700.05 miles (108,952.67 km)
·
One minute along
orbit of Sun: 1129.283 miles (1817.405 km)
Sumber
Labels:
Mathematician
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