Page 35 - Ganit Kaushal

2 Lines and Angles

2.1 INTRODUCTION Learning Outcomes

By the end of this chapter, students will be able to:
Geometry is all around us; whether we look at the sides • Differentiate between a line, a line segment, and
or corners of a table, the hands of a clock, railway tracks, a ray.
racing tracks, road strips for traffic division, or grown-up • Identify and describe different types of lines, such
trees, we interact with lines and angles. as parallel and perpendicular lines.
• Recognise and classify angles based on their
In this chapter, we will learn how to define, identify, and measure (acute, right, obtuse, etc.).
measure lines and angles. Also, we will explore how they • Measure angles accurately using a protractor.
are related to each other. • Solve problems involving lines and angles to
understand real-world scenarios.

Railway Tracks Table
Tree (Lines) Running Tracks (Lines) Road Strips (Lines) (Lines & Angles) (Lines & Angles)
2.2 BASIC GEOMETRICAL CONCEPTS AND THEIR DEFINITIONS

Points

A point in geometry is a location that is represented by a small dot. It has no size, A B
that is, no length, width or height. Points are usually denoted by capital letters of the
English alphabet, such as A, B, C, etc. In the adjacent figure, there are three points,
represented by A, B and C. These points are read as ‘point A’, ‘point B’ and ‘point C’. C

Line Segment

A line segment is defined as the shortest route between any two distinct points on a plane. B

In the given figure, two points, say A and B, are joined by four different routes.
Which one is the shortest path joining points A and B?
A
Yes, you identified it correctly; it is the third from the top. So, this is known as
the line segment joining points A and B. Note that line segment AB is the same B
as line segment BA. They are also denoted by putting a bar on them. So, AB is A
read as ‘line segment AB’.
The points A and B are called the end points of AB.

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