Trigonometry is a branch of mathematics that deals with sides and angles of a triangle. It has many identities. These identities are commonly used for writing different types of trigonometric expressions. Sumerian astronomers studied measures of angles by dividing a complete angle in 360 equal parts. Hellenistic mathematicians like Euclid and Archimedes studied properties of chords and inscribed angles inside a circle. They also proved theorems similar to the modern trigonometric formulae. In h