He further stated:
Using ciphers (Arabic for zero), the Arabs became the founders of the arithmetic of everyday life; they made algebra an exact science. The Arabs kept alive higher intellectual life and the study of science when the Christian West was fighting desperately with barbarism.
According to Gerard De Vaucouleurs, in his book, Discovery of the Universe, Page 35. Al Battani (939-998) was a great astronomer and mathematician. He published an original Almagest and developed trigonometry science, and discovered the moon’s motion’s inequality known as the variation.
Gerard De Vaucouleurs, further said:
Abattani made new observations for the sun’s position, improved the value of the tropical year, rectified Ptolemy’s precession constant, and measured the elliptic’s obliquity with care. He introduced the sine into trigonometry.
Albattani composed a work on astronomy, with tables, containing his own observations of the sun and moon and a more accurate description of their motions than that given in Ptolemy’s “Almagest.” In it moreover, he gives the motions of the five planets, with the improved observations he succeeded in making and other necessary astronomical calculations.
Some of his observations mentioned in his book of tables were made in the year 880 and later on in the year 900. Nobody is known in Islam who reached similar perfection in observing the stars and scrutinizing their motions.