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.

types of angles

  1. Acute angle: When an angle measures between 0° and 90° it is called an acute angle.
    acute angle
  2. Right angle: When the angle is exactly equal to 90°, it is called right angle.

    right angle
  1. Obtuse angle: When an angle measures between 90° and 180°. It is called an obtuse angle.
    obtuse angle
  1. Straight angle: When an angle measure exactly 180° it is called straight angle.”
    straight angle
  1. Reflex Angle: When an angle is greater than 180° but less than 360°.Then it is called Reflex angle.
    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.
    adjacent anglesHere, 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.
    linear pair∠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.
    vertically opposite angleLet 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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