# Introduction to Trigonometry

Trigonometry is an important branch of mathematics. The word trigonometry is derived from three Greek words: **t****ri** (three), **g****oni **(angles), **m****etron** (measurement). It literally means “**measurement of triangles.**”

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

For the 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.