**Introduction**

**Trigonometry is an important branch of mathematics.**

** Trigonometry is a Greek word. The word Trigonometry has been divided into three phases.**

**Tri** mean **THREE**

## **G**oni mean** ANGLES**

## **Metron** mean **MEASUREMENT**

**It is clear that Trigonometry means** **Measurement of a triangle.**

**Unit of Measures of Angles.**

**What is Angle.**

**Two rays have the same initial points make an angle with each other.****The starting point is called the initial point and the other is called the ending point or terminating point.**

**Property of Triangle**

- The
**hypotenuse**is always the**longest side**and it is the**opposite of the right-angle**. - The
**opposite**side of the triangle that side isto the*opposite***angle**. - The
**adjacent**side is the side that isthe**adjacent to****angle**. - The
**greatest side**is opposite to the**greatest angle.** - The
**smallest side**is opposite to the**smallest angle.** - you can check the
**Rotation of axes**for further concepts.