Page 93 - Cambridge Checkpoint Mathematics Coursebook 7_Slide 02

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.

Th 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. Th 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.

F 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