Page 199 - ICSE Math 7

18 Symmetry, Reflection

and Rotation

Key Concepts

• Symmetry • Reflection
• Line(s) of Symmetry of Geometrical Figures • Rotation

There is another way to look at the world around us. We can see countless examples 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.
In this chapter, we will learn about symmetry and line(s) of
symmetry of geometrical figures. We will also learn about
reflection and rotation.
Some examples of symmetry which we come across every
day around us are given alongside.

Let’s observe the lines of symmetry in the following figures.

Symmetry

A geometrical figure or an object is said to be symmetric if its one half L
is of exactly the same size and shape as the other half. A geometrical A H
figure or an object which is identical about a line passing through it C B G F
is said to have linear symmetry and the line is known as the line of
symmetry or axis of symmetry. If we fold a symmetric figure along
the line of symmetry, then the two parts of the figure will coincide.
In the adjoining figure, an octagon ABCDEFGH is shown which is D E
symmetrical about line LM. Thus, LM is the line of symmetry of the M
given octagon. line of symmetry

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