(full name, Abu Abdallah Muhammad ibn Jabir). Born 858; died 929. Arab astronomer-observer. Native of Battan (Syria).
From 877 to 918 al-Battani carried out astronomical observations in Rakka and made new and more precise determinations of the precessional constant and angle of inclination of the ecliptic to the equator. He introduced the use of trigonometric functions—sine, tangent, and cotangent.