The history of trigonometry dates back to the early ages of Egypt and Babylon . Angles were then measured in degrees. History of trigonometry was then advanced by the Greek astronomer Hipparchus who compiled a trigonometry table that measured the length of the chord subtending the various angles in a circle of a fixed radius r.This was done in increasing degrees of 71.In the 5 th century, Ptolemy took this further by creating the table of chords with increasing 1 degree. 
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The earliest uses of trigonometry functions were related to the chords of a circle and recognition that the length of chord substended by a given angel x was 2sin(x/2). the greek astronomer and mathematician Hipparcus produced the first known table of chords.