Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles.

Scalene triangles have three different-sized angles and three different-sized edges (sides).

Isosceles triangles have two equal-sized angles and two sides of the same length.

A right-angled triangle has exactly one 90° interior angle.

Formalising understanding of triangles from KS2

Maths

Checking understanding of angles from KS2

Securing understanding of angles from KS2

Formal angle notation

Corresponding angles

Alternate angles

Co-interior angles

Angles on parallel lines traversed by a straight line

The sum of the interior angles of any triangle

Using the sum of the interior angles of a triangle

Interior angles of a polygon

Deriving the sum of interior angles in multiple ways

Exterior angles of polygons

Interior and exterior angles of regular polygons

Missing angles

Problem solving with polygons

This unit gives pupils the opportunity to explore polygons and begin to generalise their understanding of interior/exterior angles in regular polygons. In the future unit, pupils will use the geometrical properties of a rhombus to perform various constructions

In this unit, pupils learnt how to calculate with angles at a point and angles on a straight line. In this unit, pupils extend their knowledge about angles in lines

In this unit pupils will investigate internal and external angles of polygons and angles made with a transveral and parallel lines. Pupils will develop their ability to formally prove properties of polygons to generalise.

Geometrical properties: polygons

Which of these statements are true about this triangle?

This triangle is scalene. Which of these are possible values of $$b$$?

It is impossible to know the size of angle $$c$$.

Which of these statements are correct for this triangle?

It is impossible to know any angles in this triangle, as none are given.

A different side of this triangle has a length of 40 cm.

A different side of this triangle has a length of 60 cm.

An equilateral triangle has one side of length 40 cm. Which of these statements are correct?

An isosceles triangle has an angle of 90°, and a side of length 19 cm. What is the size of one of its other angles, in degrees? {{}}°.

impossible to have this triangle with an angle of 30°

Three different triangles each have an angle of 30°. Match the name of each triangle to their possible angles.

These three angles lie around a point on a full turn. $$b$$° = {{}}°.

Angle $$c$$° and 42° are vertically opposite.

Angle $$c$$° and 42° are supplementary.

This diagram shows four angles around two line segments that meet at an intersection. Which of these statements are correct for angle $$c$$°?

Angle $$d$$° and 42° are vertically opposite.

Angle $$d$$° and 42° are supplementary.

This diagram shows four angles around two line segments that meet at an intersection. Which of these statements are correct for angle $$d$$?

PQ and RS are straight line segments. $$e$$° = {{}}°.

PQ and RS are straight line segments. Match each angle to its size.

Formalising understanding of triangles from KS2

Lesson outcome