Habash al-Hasib's tangent and cotangent tables
Tablas de tangente y cotangente de Habash al-Hasib
- Date
- c. 850 · confidence medium
- Place
- Baghdad, Iraq
- Credited to
- Habash al-Hasib al-Marwazi (a native of Merv)
- Field
- Knowledge & symbols
What was discovered
The Merv astronomer computed tables of «shadows» equivalent to the tangent and cotangent of an angle, to solve astronomy and sundial-time problems. They are the first known use of the tangent as a trigonometric function in the Islamic world.
He is credited with the first tangent table, but the concept of the gnomon shadow has Indian precedents; the date of composition is approximate.
What it led to
- six-function trigonometry of the 10th-11th centuries (al-Battani, Abu al-Wafa)
- calculations of time and the qibla direction
- the astronomical tables (zij) of Baghdad