Who discovered Trigonometry?

[Joffe]

I have read that astronomers are responsible for much of the advances in trig hundreds of years ago but never seem to find who exactly pioneered this field of research.

[fourier jr]

The first work on trigonometric functions related to chords of a circle. Given a circle of fixed radius, 60 units were often used in early calculations, then the problem was to find the length of the chord subtended by a given angle. For a circle of unit radius the length of the chord subtended by the angle x was 2sin (x/2). The first known table of chords was produced by the Greek mathematician Hipparchus in about 140 BC. Although these tables have not survived, it is claimed that twelve books of tables of chords were written by Hipparchus. This makes Hipparchus the founder of trigonometry.
http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Trigonometric_functions.html

i guess the 2sin(x/2) isn't what the greeks called it; that's what it's called in modern terminology

[robert Ihnot]

I notice we don't have many people on this one. WELL, when I was in high school, I was told that THALES (Thales the Milesian) Ca 635BC-543BC was a businessman who traveled to Egypt and decided to write up and systemize their geometry, which was used for ownership decisions after the Nile overflowed.

I quote: Thales is credited with first popularizing geometry in ancient Greek culture, mainly that of spatial relationships. He is the first one who separated trigonometry as an independent group from Mathematics, to be one of the four basic "elements" of geometry http://en.wikipedia.org/wiki/Thales