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)