NCERT 6TH CLASS MATHEMATICS CHAPTER BASIC GEOMETRICAL IDEAS
The English word Geometry has been derived from the Greek woud geometron which means to measure the Earth'. Geometrical idea have developed over centuries to cater to needs in art, architecture etc. Here, we will discuss some basic concepts in geometry.
A point shows an exact location of an object. It is the basic unit of geometry. It is represented with the help of a dot. It is named by using a single capital English alphabet.
LINE, LINE SEGEMENT, AND RAY
A line is a collection of points going endlessly in both directions along a straight path.
The symbol for a line is «.
The arrows show that line goes on endlessly in both directions. A and B are two points on the line.
We call it line AB and write it as or . It can also be named by means of any small English letter, say l.
(a) Intersecting Lines :
If two or more lines meet each other at one point then they are called intersecting lines. Two intersecting lines have one common point.
(b) Parallel Lines :
If two or more lines do not meet each other however far they are extended, then they are called parallel lines.
The opposite edges of a book, table, ruler etc. are good examples of parallel lines.
(c) Line segment :
A line segment is part of a line. It has two endpoints and has a fixed legnth.
We name the segment by its endpoints.
The symbol for a line segment is "_____" .
Points P and Q are the two endpoints of the line segment PQ as shows above. We write it as or .