Class 8 Maths Chapter 3 Understanding quadrilaterals exercise 3.1 pdf notes:-

**Exercise 3.1** Class 8 maths Chapter 3 Pdf Notes:-

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## Ncert Solution for Class 8 Maths Chapter 3 Understanding quadrilaterals Exercise 3.1 Tips:

**Introduction**

You know that the paper is a model for a plane surface. When you join a number of

points without lifting a pencil from the paper (and without retracing any portion of the

drawing other than single points), you get a plane curve.

Try to recall different varieties of curves you have seen in the earlier classes.

Match the following: (Caution! A figure may match to more than one type).

Convex and concave polygons

Here are some convex polygons and some concave polygons. (Fig 3.3)

**Convex polygons Concave polygons**

Can you find how these types of polygons differ from one another? Polygons that are

convex have no portions of their diagonals in their exteriors. Is this true with concave polygons?

Study the figures given. Then try to describe in your own words what we mean by a convex

polygon and what we mean by a concave polygon. Give two rough sketches of each kind.

In our work in this class, we will be dealing with convex polygons only. Regular and irregular polygons

A regular polygon is both āequiangularā and āequilateralā. For example, a square has sides of

equal length and angles of equal measure. Hence it is a regular polygon. A rectangle is

equiangular but not equilateral. Is a rectangle a regular polygon? Is an equilateral triangle a

regular polygon? Why?

In the previous classes, have you come across any quadrilateral that is equilateral but not

equiangular? Recall the quadrilateral shapes you saw in earlier classes ā Rectangle, Square,

Rhombus etc.

Is there a triangle that is equilateral but not equiangular?

3.2.5 Angle sum property

Do you remember the angle-sum property of a triangle? The sum of the measures of the

three angles of a triangle is 180Ā°. Recall the methods by which we tried to visualise this

fact. We now extend these ideas to a quadrilateral.