*Angles:- **Angle is the union of two rays with a common end point.*

** When two rays in a plane meet at a point, an angle is formed.*

** The two rays forming an angle are called the arms or sides of the angle.*

*The amount of rotation performed by a ray with its end point fixed either in clockwise or anti clockwise direction is also be called as **“Angle”.*

** The ray which is in a fixed position is called the **initial ray** and the position of the rotating ray is called the **terminal ray.*

* *The common end point of the two rays forming an angle is called the vertex of the angle.*

**An angle whose measure is more than 0 ^{0} but less than 90^{0} is called an Acute angle.**

**An angle whose measure is 90 ^{0} is called an Right Angle: **

**An right angle is exactly one quarter of a revolution.**

**An angle whose measure is more than 90 ^{0} but less than 180^{0} , is called an Obtuse Angle.**

**An angle whose measure is 180 ^{0}, is called an Straight angle.**

**A straight angle is exactly one half of a revolution.**

**An angle whose measure is more than 180 ^{0} but less than 360^{0} is called an Reflex Angle.**

**An angle whose measure is 360 ^{0}, is called an Complete Angle**

**If the terminal ray coincides with the initial ray after one complete rotation. Then the angle formed is called a complete angle.**

**If the terminal ray coincides with the initial ray, without any rotation. Then the angle formed is called ‘zero angle’.**

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**If the measure of the angle is 0 ^{0} it is called a zero angle.**