Page 217 - Start Up Mathematics_7
P. 217
13 Reflection and Rotational Symmetry
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. India Gate
Line Symmetry
A figure has line symmetry, if it can be divided by a
line into two equal halves, each of which is the mirror
image of the other. If the figure is folded about the line of
symmetry, the two halves of the figure coincide precisely.
Some examples of symmetry which we come across every
day in things around us are given alongside. Leaf Mask
Let’s find the lines of symmetry in the following figures:
Most of the figures have either one or two lines of symmetry. Lines of symmetry are usually
vertical, horizontal or oblique. Some figures like squares have four lines of symmetry. A circle
has infinite lines of symmetry.
