Reasoning about angles in polygons

Maths

In this unit pupils will compare the size of angles where there is a clear visual difference and use the terms acute, obtuse and reflex when describing the size of angles or amount of rotation with relation to right angles using a unit called degrees. In the future unit pupils will use knowledge of shape properties to draw, sketch and identify shapes.

In the prior unit pupils completed and composed symmetrical shapes from two congruent shapes and investigate lines of symmetry in 2D shapes. In this unit pupils will compare the size of angles where there is a clear visual difference and use the terms acute, obtuse and reflex when describing the size of angles or amount of rotation with relation to right angles using a unit called degrees.

Angles: compare, name, estimate and measure angles

The markers divide each line into two parts.

What do these lines represent on two sides of this polygon?

Any polygon can be always be divided into what other type of polygon?

Multiplying the number of internal triangles by 180

You can work out the sum of the angles in a polygon by:

The size of missing angle a is {{ }} degrees.

A triangle is placed inside a rectangle. Tick the calculation that helps to find missing angle b.

A triangle is placed inside a rectangle. The size of missing angle c is {{ }} degrees.

Look at the hands on this clock face and the arrow. The angle formed is __________.

Where two lines create an angle within a shape, we call this part a {{ }}.

The angles in a quadrilateral sum to ___.

Fill in the missing product
3 × 180 = {{ }}

The triangle is not to scale. The missing angle labelled m is {{ }}°

This lesson will soon be taken down.

Reasoning about angles in polygons

Lesson outcome