## Ncert Solutions for Class 6 Maths Chapter 4 Basic Geometrical Ideas Exercise 4.2:

**Exercise 4.2**Ā Class 6 maths NCERT solutions Chapter 4 Basic Geometrical Ideas Exercise 4.2 Pdf Download:-

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CLASS-6 Ex. 4.2 Basic Geometrical Ideas Free pdf Ncert Textbook Solutions

**A Line:**

Imagine that the line segment from A to B (i.e. AB) is extended beyond A in

one direction and beyond B in the other

direction without any end (see figure). You

now get a model for a line.

Do you think you can draw a complete picture of a line? No. (Why?)

A line through two points A and B is written as AB.

It extends indefinitely in both directions. So it contains a

countless number of points. (Think about this).

Two points are enough to fix a line. We say ātwo

points determine a lineā.

The adjacent diagram (Fig 4.3) is that of a line

PQ written as PQ. Sometimes a line is denoted by

**Curves**

Have you ever taken a piece of paper and just doodled? The pictures that

are results of your doodling are called curves.

You can draw some of these drawings without lifting the pencil from the paper

and without the use of a ruler. These are all curves.

āCurveā in everyday usage means ānot straightā. In Mathematics, a curve

can be straight like the one shown in fig 4.10 (iv).

Observe that the curves (iii) and (vii)Ā cross themselves,

whereas the curves (i), (ii), (v) and (vi) do not. If a curve does

not cross itself, then it is called a simple curve.

Draw five more simple curves and five curves that are not simple.

Consider these now (Fig 4.11).

What is the difference between these

two? The first i.e. Fig 4.11 (i) is an

open curve and the second i.e. Fig 4.11(ii)

is a closed curve. Can you identify some

closed and open curves from the figures

Ā (i), (ii), (v), (vi)? Draw five curves

each that are open and closed.

Position in a figure

A court line in a tennis court divides it into three parts : inside the line, on the

line and outside the line. You cannot enter inside without crossing the line.

A compound wall separates your house

from the road. You talk about āinsideā the

compound, āonā the boundary of the

compound and āoutsideā the compound.

In a closed curve, thus, there are three parts.

(i) interior (āinsideā) of the curve

(ii) boundary (āonā) of the curve and

(iii) exterior (āoutsideā) of the curve.

In the figure 4.12, A is in the interior, C is in the exterior and B is on

the curve.

The interior of a curve together with its boundary is called its āregionā.

**Polygons:-**

So, a figure is a polygon if it is a simple closed figure made up entirely

of line segments. Draw ten differently shaped polygons.