Rotational symmetry describes when a shape appears the same after some rotation. The order of rotational symmetry is the number of times the image appears the same as the object in one full turn.

Rotational symmetry

Maths

Checking understanding of similarity

Checking understanding of congruence

Similarity in shapes

Congruence in shapes

Congruent, similar or neither

Congruent triangles (SSS)

Congruent triangles (SAS)

Congruent triangles (ASA and AAS)

Congruent triangles (RHS)

Applying the criteria for congruence

Demonstrating Pythagoras' theorem

Further demonstrating of Pythagoras' theorem

Length of the hypotenuse

Length of a shorter side

Determining which side

Pythagoras' theorem in context

Problem solving with similarity and Pythagoras' theorem

In this unit, pupils continued to build on their understanding of congruence and similarity with right-angled triangles. In the future unit, similarity is used to extend a right-angled triangle in the unit circle to any other right-angled triangle.

In the prior unit, pupils explored the effects of different transformations and whether the transformed shape was congruent or similar to the original shape. This is built on in this unit where pupils formalise the criteria for determining congruence in triangles and study rotational symmetry.

This unit explores the concepts of congruence and similarity, and ways to prove or disprove similarity between shapes. We then explore further properties of triangles with Pythagoras' Theorem.

Geometrical properties: similarity and Pythagoras' theorem

Rotational {{}} describes when a shape appears the same after some rotation.

An equilateral triangle has rotational symmetry of order {{}}.

A scalene triangle has rotational symmetry of order {{}}.

Which of these quadrilaterals always has rotational symmetry of order 4?

The wheel in this picture has rotational symmetry of order {{}}.

isosceles triangle (that is not equilateral)

Starting with the lowest, order these shapes according to their order of rotational symmetry.

The transformation that turns an an object around a fixed point is called {{}}.

The {{}} is the fixed point about which an object is rotated.

There are exactly five equal sized angle around a point. Each angle is {{}}°.

The arrow on the left can be rotated {{}}° clockwise to create the arrow on the right.

The rectangle ACDB is rotated to give rectangle D'B'A'C'. The angle of rotation is {{}}°.

Rotational symmetry

Lesson outcome