Mathematician and member of the University of Alexandria from 125 to 160 and author of the Almageste (name of Arabic origin meaning “the greatest”). This work on astronomy acquired the same reputation as Euclid’s Elements in geometry.
Ptolemy’s Almageste has stood the test of time. In his works on astronomy and trigonometry, Ptolemy divided the circle into 360° and the diameter into 120 parts, then each part into minutes, seconds and thirds, in the same manner as the sexagesimal system of the Babylonians.*
* Source: Jean-Paul Colette, Histoire des mathématiques, tome 1, ERPI, p.93