*Introduction to Trigonometry.

Trigonometry is a branch of Mathematics that deals with the relation between sides and angles of triangles. The word ‘trigonometry’ is derived from the Greek words ‘trigonon’ and ‘metron’. It means measuring the sides of triangles. Greek Mathematicians used trigonometric ratios to determine unknown distances. The Egyptians used a primitive form of trigonometry for building pyramids in the second millennium BC. Greek astronomer Hipparches (190-120 BC) formulated the general principles of trigonometry and he is known as the founder of the trigonometry. We are familiar with trigonometric ratios of acute angles a in right angled triangle. We have introduced the concept of directed angle having any measure, in the previous chapter. We shall now extend the definitions of trigonometric ratios to angles of any measure in terms of coordinates of points on the standard circle.

*Trigonometry = It can be understand in six ways.

1. Trigonometry function with the help of unit circle.
2. Extensions of Trigonometry Functions to any angle.
3. Range and Signs of Trigonometry Functions in different quadrants.
4. Fundamental Identities and Periodicity of Trigonometric Functions.
5. Domain, Range and Graph of each Trigonometry Function.
6. Polar Co-Ordinates.