Habash al-Hasib al-Marwazi died after 869 AD

He flourished in Baghdad . He was a great astronomer, geographer, and mathematician He described first time Trigonometric ratios: SIN, COS, TAN & COT.

He made observations from 825 to 835, and compiled three astronomical tables: 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 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)