Symmetry & Shapes (Edexcel GCSE Maths: Foundation): Flashcards

A shape is said to have rotational symmetry if, during a 360° rotation about its centre, it looks the same as it did in its original position.

The order of rotational symmetry refers to the number of times a shape looks the same as it is rotated 360° about its centre.

False.

A shape can never have order 0 rotational symmetry.

A shape is said to have no rotational symmetry when the order of rotational symmetry is 1, i.e. it only looks like its original position when it has been rotated through the full 360°.

You can use tracing paper to help you work out the order of symmetry for a particular shape by doing the following:

1. Sketch the shape onto the tracing paper.

2. Draw an arrow pointing upwards on the tracing paper.

3. Place your pencil in the centre of the shape and rotate the tracing paper until the arrow is pointing upwards again (360º).

4. Count how many times the shape on the tracing paper maps over the shape on the paper beneath exactly; this is the order of rotational symmetry.

A shape is said to have line symmetry when one half of the shape is a mirror image of the other half.

A line of symmetry is a line across which a shape can be folded or reflected so that the two halves match exactly.

True.

A line of symmetry is also known as a line of reflection.

It can also be called a mirror line.

You can use tracing paper to help you sketch the reflection of a shape:

1. Trace the shape and the line of symmetry on the tracing paper.

2. Flip the paper over the line of symmetry.

3. The traced image will now be in its reflected position.

A plane of symmetry in a 3D shape is a plane (flat 2D shape) that splits a 3D shape into two congruent (identical) halves that are mirror images of each other.

A cube has 9 planes of symmetry.