Hipparchus

Hipparchus /hɪˈpɑːrkəs/ of Nicaea, or more correctly Hipparchos (Greek: Ἵππαρχος, Hipparkhos; c. 190 BC – c. 120 BC), was a Greek astronomer, geographer, and mathematician of the Hellenistic period. He is considered the founder of trigonometry but is most famous for his incidental discovery of precession of the equinoxes.