Many historians refer to Hipparchus as the father of trigonometry, according to the New Mexico Museum of Space History. Hipparchus was born in about 190 B.C., and he spent most of his life in Rhodes, Greece.
Hipparchus developed a table of chords and used his trigonometric methods to calculate eclipses of the sun and moon. He also created the first listing of stars, dividing them into classes of brightness, a revised system that is still used by modern astronomers. Hipparchus also was the first individual to define a circle as 360 degrees. Much of his life's work centered around trying to accurately determine the length of a year.