Rotational Symmetry (Edexcel IGCSE Maths)

Spec point — 4.3A

Rotational symmetry

What is the order of rotational symmetry?

• Rotational symmetry refers to the number of times a shape looks the same as it is rotated 360° about its centre

• This number is called the order of rotational symmetry

• Tracing paper can help work out the order of rotational symmetry

  • Draw an arrow on the tracing paper so you can easily tell when you have turned it through 360°

• Notice that returning to the original shape contributes 1 to the order

  • This means a shape can never have order 0
  • A shape with rotational symmetry order 1 may be described as not having any rotational symmetry
  • The only time it looks the same is when you get back to the start

Exam Hint Remember to use the trick above; using an upwards arrow on the tracing paper to show the starting orientation of the shape.

Worked Example For the shape below, shade exactly 4 more squares so that the shape has rotational symmetry of order 4.

Answer:

The shape below appears the same 4 times if rotated through 360 degrees