Page 92 - Mathematics Coursebook

8.3 Recognising rotational symmetry

8.3 Recognising rotational symmetry

A shape has rotational symmetry if it can be rotated about a point to another position and
still look the same.

!e order of rotational symmetry is the number of times the shape looks the same in one full turn.

A rectangle has rotational symmetry of order 2. !is button has rotational symmetry of order 4.

Worked example 8.3

Write down the order of rotational symmetry of each of these shapes.
a b

a Order 2 The parallelogram looks the same after a half-turn and a full turn, so has order 2.
b Order 1 The trapezium only looks the same after a full turn so has order 1.

) Exercise 8.3

1 Write down the order of rotational symmetry of these shapes.
a b c

d e f

2 Sort these cards into their correct groups.
Each group must have one blue, one green and one yellow card.
B
A Scalene
a Order of triangle
Rectangle
rotational
symmetry is 3 i
b Order of
C
Equilateral rotational
triangle symmetry is 2
ii
ii
c Order of
rotational
symmetry is 1

8 Symmetry 91