Al Battani (ca. 858-929) also known as Albatenius was an astronomer and mathematician from Arabia. Al Battani full name: Abū Abdullāh Muhammad ibn Jābir ibn Sinān ar-Raqqī al-Harrani as-Sabi al-Battānī), was born in Harran near Urfa.
One of his famous achievements in astronomy is about the determination of the Sun Year as 365 days, 5 hours, 46 minutes and 24 seconds.
Al Battani also found a number of trigonometric equations:
trigonometric equations - AL-BATANI
It also solves the equation sin x = a cos x and finds the formula:
equation sin x = a cos x - AL-BATANI
and using al-Marwazi's notion of tangent in developing equations for calculating tangent, cotangen and compiling tangent count tables.
Al Battani works in Syria, precisely in ar-Raqqah and in Damascus, which is also the place of his death.
Thanks...
....