Trigonometry is an important branch of Mathematics. The word Trigonometry has been derived from three Greek words **Tri** (Three), **Goni **(Angles), **Metron** (Measurement).

Literally it means “**measurement of triangles**”

The origin of trigonometry have been traced back to the Egyptians of the 13 century B.C., whose tables of shadow lengths correspond to today's tangent and cotangent functions. The Babylonians and Greeks trigonometry to study of heavens. Travelers of recent centuries used trigonometry to navigate, and physicist use trigonometry to study sound, light, and other waves.

For study of calculus it is essential to have a sound knowledge of trigonometry. It is extensively used in Business, Engineering, Surveying, Navigation, Astronomy, Physical and Social Sciences.