A polygon is a flat (2D), closed figure made up of straight line segments.

A regular polygon has sides that are all equal and interior (inside) angles that are all equal.

An interior angle is an angle formed inside a polygon by two of its edges.

Checking and securing understanding of interior angles

Maths

In this unit, pupils applied their understanding of angles to solve increasingly complex problems. In the future unit, pupils will use their mathematical reasoning to derive and use various circle theorems. 

In the prior unit, pupils learnt how to identify corresponding, alternate and co-interior angles. In this unit, pupils use their knowledge of these angles to reason through and solve more complicated problems.

Angles

Two of the interior angles of a triangle are 80° and 45°.  The size of the third interior angle is {{}}°.

The interior angles of a pentagon sum to {{}}°.

Each interior angle of a regular hexagon is {{}}°.

A regular polygon has interior angles of size 150°. The polygon has {{ }} sides.

Which of these interior angles are possible in a regular polygon?

One of the interior angles in an isosceles triangle is 70°. Which are possible sizes for one of the other interior angles?

Angles that meet at a single point on a straight line sum to {{}}°.

Angles are __________ if they sum to 180°.

Two angles meet to form a straight line. One angle is 60°. The other angle is {{}}°.

Squares and equilateral triangles are examples of __________ polygons.

A regular octagon has an edge with length 5 cm. Therefore, its perimeter is {{}} cm.

A regular decagon has a perimeter of 40 cm. Therefore, each of its edges are of length {{}} cm.

This lesson will soon be taken down.

Checking and securing understanding of interior angles

Lesson outcome