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Angle

When two rays or straight lines meet or intersect at a point, they form an angle.

The rays forming the angle are called the arms of the angle.

The common point is called the vertex of the angle. A
Arm
In the given figure, OA and OB are arms of the angle AOB. O is

the vertex of the angle AOB. The vertex of the angle is always Angle
written in the middle. O Arm B
Vertex
Take an A4 sheet and fold it in half horizontally and mark the crease. Right

Then, fold the sheet in half vertically and mark the crease. Unfold the Angle
sheet and observe carefully.

We observe that both the creases intersect each other at a point and

form an angle called a Right Angle.

An angle less than a right Right angle An angle more than a right
angle is an Acute angle. angle is an Obtuse angle.

D A P

Acute angle Right angle Obtuse angle
E F B C Q R

Also, the creases intersecting at a right angle represent perpendicular lines.

Think Tank Critical Thinking
1. Where do you see angles around you?
2. I run side by side with my twin on two lines and never meet, no matter how far we go. What
kind of lines are we running on?
3. When I meet another line, we form a perfect ‘L’. What are we called?

Practice Time 7B

1. Identify parallel, perpendicular and intersecting lines in the following figures.

(a) (b) (c)

(d) (e) (f)

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