# Types of Angles

In this section we will study different types of angles. Understanding the concept of angles is extremely important. They are the base for mensuration and geometry.

#### Let us look at them-

Angle: When two rays originate from a same end point they form an angle. 1. Acute angle: When an angle measures between 0° and 90° it is called an acute angle. 2. Right angle: When the angle is exactly equal to 90°, it is called right angle. 1. Obtuse angle: When an angle measures between 90° and 180°. It is called an obtuse angle. 1. Straight angle: When an angle measure exactly 180° it is called straight angle.” 1. Reflex Angle: When an angle is greater than 180° but less than 360°.Then it is called Reflex angle. 2. Full rotation or complete angle: When the angle is exactly 360° then it is called a complete angle or a full rotation.

#### Other Types of Angles

• Complementary angles: When the sum of two angles is 90°, Then they are called complementary angles.

• Supplementary angles: When the sum of two angles is 180°, Then they are called supplementary angles.

• Adjacent angles: Two angles are said to be adjacent when they have same vertex and a common arm. Also the non common arm should be on different sides of the common arm. Here, OB is the common arm.
O is the common vertex.
and OA and OC are the non common sides in different side of common arm.
∠AOB and ∠BOC are adjacent angles.

• Linear pair angles: When the non-common arms of adjacent angles form a line then the angles are called linear pair of angles. ∠AOB and ∠BOC are Linear pair angles and ∠AOB + ∠BOC = 180°

• Vertically Opposite Angles: When two lines intersect each other , two pair of vertically opposite angles are formed. Let us say,
AB and CD intersect each other at O.
Here
∠AOC and ∠BOD are vertically opposite angles.
and ∠AOD and ∠BOC are also vertically opposite angles.

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