[NCERT] Class 8 Maths Quadrilateral Ex 3.1 Solutions

[NCERT] Class 8 Maths Ex 3.1 Solutions (2024-25)

Solution:-

(a) Simple Curve:- (1), (2), (5), (6), (7)

(b) Simple Closed Curve:- (1), (2), (5), (6), (7)

(c) Polygon:- (1), (2)

A simple closed curve made up of only line segments is called a polygon.

(d) Convex Polygon:- (2)

(e) Concave Polygon:- (1)

Explanation:-

What is Plane (simple) Curve

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.

In other words, a simple curve that changes direction but does not cross itself while changing direction.

Remember two things to form a simple curve.

Don’t lift the pencil while joining the different point on paper.

Don’t cross and retrace (go back over something) any portion of the drawing other than the single point.

Note:-

(3) is not a simple curve, as there are two circle, to draw a second circle we have to lift the pencel.

(4) is not a simple curve, as the line joining two points are crossing each other.

(8) is not a simple curve, as to draw such figure, one either has to lift the pencil or line joining the points will retrace each other.

Q. 2

What is regular polygon? State the name of a regular polygon of

(i) 3 sides

(ii) 4 sides

(iii) 6 sides

Answer:-

A regular polygon is both ‘equiangular’ (all angles equal)  and ‘equilateral’ (all sides equal).

In simple words, regular polygon has its all angles equal and all its sides of equal lengths.

For example:- Square, equilateral triangle.

(i) 3 sides regular polygon = Equilateral triangle

(ii) 4 sides regular polygon = Square

(iii) 6 sides regular polygon = Regular Hexagon