# Class 8 Maths Chapter 3 Exercise 3.1 Pdf Notes NCERT Solutions

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

Exercise 3.1 Class 8 maths Chapter 3 Pdf Notes:-

## 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 āequiangularā and āequilateralā. 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.