Hipparchus in Harpers Dictionary of Classical Antiquities

1. A son of Pisistratus. (See Pisistratidae.) 2. A Greek mathematician, the founder of scientific astronomy. He was born at Nicaea in Bithynia about B.C. 160, lived chiefly at Rhodes and Alexandria, and died about B.C. 120. He discovered the precession of the equinoxes, settled more accurately the length of the solar year, as also of the revolution of the moon, and the magnitude and distances of the heavenly bodies. He placed mathematical geography on a firmer basis, by teaching the application of the latitude and longitude of the stars to marking the position of places on the surface of the earth. He is also regarded as having invented trigonometry. In plane trigonometry he constructed a table of chords of arcs, which is practically the same as one of natural sines; and in spherical trigonometry he had some methods of solving triangles. Of his numerous writings we possess only his commentary on the Phaenomena of Eudoxus and Aratus and a catalogue of 1026 fixed stars. The famous Almagest of Ptolemy (Μεγίστη Σύνταξις) is founded on the writings of Hipparchus. See Ball, Short Hist. of Mathematics, pp. 79-81, 90 (London, 1888).