Page 187 - Maths Skills - 7

Symmetry 185

INTRODUCTION
In the previous class, we have studied about lines of symmetry. We have seen presence of symmetry in man-made
things as well as in nature. Buildings, jewellery, mathematical figures and some designs may exhibit symmetry.
Nature has also gifted us with some of the most astonishing and perfect examples of objects possessing symmetry.
Tree leaves, flowers, beehives, fish, insects, animals, etc. look balanced and beautiful because of symmetry.
Artists, architects, designers, mathematicians and many others use it in different activities related to their work.

SYMMETRY A

A figure is said to be symmetrical about a line or axis if it is identical on either side of
it. The line which divides the figure into two equal halves is called the line of symmetry
or axis of symmetry. For example, line AB divides the Fig. into two identical halves.
Here, AB is the axis of symmetry. This kind of symmetry is referred to as linear
symmetry.

Line of Symmetry
A figure may have a line or lines of symmetry. B

For example;
A square has four lines of symmetry. A rectangle has two lines of symmetry.

Symmetry in Regular Polygons
Since a regular polygon has all its sides and angles equal, it has many lines of symmetry. In fact, the number of
lines of symmetry are same as the number of sides.

Number of Lines of
Polygon Lines of Symmetry
Symmetry

Equilateral Triangle
3

Square 4

Pentagon 5

Fact-o-meter
Hexagon
6 The number of lines of
symmetry in the regular
polygons will be equal
Heptagon to number of sides in
7
that regular polygon.