Page 11 - Cambridge IGCSE Mathematics Core and Extended

When we rotate the diagram through 180°, it fits exactly its original shape. When we rotate through
another 180°, it fits too. We say such diagram has rotational symmetry of order 2.
The following diagrams have rotational symmetry of other orders:

TIPS
If a figure fits its original
shape once only after a full
rotation, we say it has no
order 3 order 4 order 5
rotational symmetry.
Example 4
For each of the following diagram, state
(i) the number of lines of symmetry,
(ii) the order of rotational symmetry.
(a) (b)

Solution
(a) (i) Number of lines of symmetry = 0
(ii) Order of rotational symmetry = 2

(b) (i) Number of lines of symmetry = 6

(ii) Order of rotational symmetry = 6

Test Yourself 11.2

1. For each of the following diagrams, (c) A (d) A D
determine the number of line(s) of symmetry

and draw the line(s) of symmetry. C D
(a) (b)
B C B

3. For each of the following diagrams, state
(c) (d) (i) the number of lines of symmetry,
(ii) the order of rotational symmetry.
(a) (b)

2. Copy and complete each of the following
diagrams if AB and CD are the lines of
symmetry. (c) (d)
(a) (b) A

A B

B

Chapter 11 Polygons I 151

14/07/2022 10:14 AM
DA1501_pg 147 to 161.indd 151
DA1501_pg 147 to 161.indd 151 14/07/2022 10:14 AM