== Ancient Indian concepts of Jya (chord) and Chaap or Dhanu (arc) ==
== Ancient Indian concepts of Jya (chord) and Chaap or Dhanu (arc) ==
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'''Jyā''', '''koti-jyā''' and '''utkrama-jyā''' are three trigonometric functions introduced by [[Indian mathematics|Indian mathematician]]s and astronomers. The earliest known Indian treatise containing references to these functions is Surya Siddhanta. These are functions of arcs of circles and not functions of angles. Jyā and kotijyā are closely related to the modern trigonometric functions of sine and cosine. In fact, the origins of the modern terms of "sine" and "cosine" have been traced back to the [[Sanskrit]] words jyā and kotijyā.<ref name="Datta" />
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'''Jyā''', '''koti-jyā''' and '''utkrama-jyā''' are three trigonometric functions introduced by [[Indian mathematics|Indian mathematician]]s and astronomers. The earliest known Indian treatise containing references to these functions is Surya Siddhanta. These are functions of arcs of circles and not functions of angles. Jyā and kotijyā are closely related to the modern trigonometric functions of sine and cosine. In fact, the origins of the modern terms of "sine" and "cosine" have been traced back to the [[Sanskrit]] words jyā and kotijyā.