Page 87 - Maths Skill - 6

Lines and Angles 85

INTRODUCTION
The word ‘Geometry’ has been derived from the Greek word ‘Geometron’ where ‘Geo’ means Earth and ‘metron’
means measurement, i.e., measurement of Earth which was required by ancient civilization for various purposes.
It was basically the need of geometrical ideas for art, architecture and other measurements. Our cultural heritage
is full of umpteen examples of beautiful temples, tombs, palaces that show the use of geometry in construction.

We are already familiar with some of the basic concepts of geometry such as points, lines, planes etc. Let’s
recapitulate them with the help of the Table 6.1.

Table 6.1

Definition of Geometrical Representation/ Figure Example
Concept Symbol

1. Point: A point is a mark of position or It is represented by •A The tip of a needle,
location on a plane. It has no length, any capital letter of (read as point A) pencil or compasses.
no breadth and no height, i.e., it is English alphabet.
zero-dimensional.

2. Line: A line is a straight path that A stretched string, a
extends indefinitely in both directions. B crease in a paper.
It has no end points. It has no definite A
↔
length. It is one- dimensional. AB (read as line AB)
or or
line l l

3. Line segment: A line segment is a Q Edge of a ruler, table or
part of a line. It has two end points blackboard.
and its length can be measured. It is P
also one-dimensional. PQ
(read as line segment
PQ)

4. Ray: A ray is a part of a line that P Sun rays, a beam of
begins from one point and extends → light etc.
indefinitely only in one direction. PQ Q
(read as ray PQ)