Name Habash al-Marwazi Role Astronomer | Died 874 AD, Samarra, Iraq | |
 | ||
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.
Contents
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: