Page 54 - Maths Class 06

Basic Geometrical Ideas (2-D)

Introduction

Geometry is the study of sets of points. When beginning any field of study, you must pay special attention
to the meanings of the words you use. When defining words, you must express them in terms of simpler
words whose meanings you already know. This means that you must begin with a few simple words that
remain undefined but whose meanings are nevertheless understood. Some undefined terms of geometry
are point, line and plane. These terms serve as a basis for defining other geometrical terms.

Point
A point is an exact location in the space. It has a position but no NOTE
magnitude (size). A dot made by a sharpened pencil or a prick made by
A point has no dimension,
a needle on a paper are simple representations of points. length, breadth or thickness.
It cannot be measured.
C
A
B
Fig. 4.1
The points are named by single capital letters of alphabet such as A, B, C,…, etc.

Line

A line is a straight path from one point to another and
extends indefinitely on both sides. The length of a line cannot NOTE
be measured. As we cannot represent a line in totality
A line is named by a single small letter of the alphabet or by on a paper, we represent a portion of it
naming any two points on the line as shown below: and draw two arrow heads at the ends
to show that they can be extended in
those directions to any length.

A B
a
Line a
AB of Line AB
Fig. 4.2

Line Segment

A line segment is the shortest straight path between any two points.
Look at these two points A and B. Three paths from A to B are given, we can draw A B
many more paths from A to B. Note that the shortest path from A to B is the straight
path. This distance is called line segment AB, and is written as AB. Fig. 4.3

Mathematics-6 54