Trigonometry (from the Greek trigonon = three angles and metro = measure) is a branch of mathematics dealing with angles of triangles and trigonometric functions such as sinus, cosine, and tangent. Trigonometry has a relationship with geometry, although there is disagreement about what the relationship is; for some people, trigonometry is part of geometry.
Early trigonometry can be traced back to the days of Ancient Egypt and Babylonian and Indus Valley civilizations, over 3000 years ago. Indian mathematicians are the pioneers of calculating algebraic variables used to calculate astronomy and also trigonometry. Lagadha is a known mathematician to this day who uses geometry and trigonometry for astronomical calculations in his Vedanga, Jyotisha, most of whose work was ruined by the Indian invaders.
The Greek Mathematician Hipparchus around 150 BC constructed trigonometric tables to solve triangles.
Another Greek mathematician, Ptolemy around the year 100 developed further trigonometric counting.
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Silesia mathematician Bartholemaeus Pitiskus published an influential work on trigonometry in 1595 and introduced this word into English and French.