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.
- Acute angle: When an angle measures between 0° and 90° it is called an acute angle.
- Right angle: When the angle is exactly equal to 90°, it is called right angle.
- Obtuse angle: When an angle measures between 90° and 180°. It is called an obtuse angle.
- Straight angle: When an angle measure exactly 180° it is called straight angle.”
- Reflex Angle: When an angle is greater than 180° but less than 360°.Then it is called Reflex angle.
- 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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