Hipparchus of Rhodes (c. 190 BC-120 BC), an ancient Greek astronomer and mathematician who made fundamental contributions to the advancement of astronomy as a mathematical science and to the foundations of trigonometry. He produced a table of chords, an early example of a trigonometric table, leading some historians to argue that he was the inventor of trigonometry. The purpose of this table of chords was to give a method for solving triangles that avoided solving each triangle from first principles. He also introduced the division of a circle into 360 degrees to Greece. Hipparchus calculated the length of the year to within 6.5 minutes, discovered the precession of the equinoxes, and made some early, careful studies of the motion of Earth's moon.
Hipparchus - Biography (University of St. Andrews, Scotland, School of Mathematics and Statistics)