-
Introduction
View the activity introduction for more information on the topic
-
Read aloud
Read the question aloud
-
Accessibility
Open the accessibility toolbar to change fonts and contrast, choose a different language, use a ruler and more
In this activity, we will be looking at regular polygons.
A regular polygon has sides that are all the same length and angles that are all equal.
As in this regular octagon below:
The following formulae for regular polygons should be known:
Exterior angle = 360º ÷ number of sides
So with the octagon above, the exterior angle is 360 ÷ 8 = 45º
Interior angle = 180º - exterior angle
So with the octagon, the interior angle is 180 - 45 = 135º
Sum of interior angles = 180 x (number of sides - 2)
So with the octagon, the sum of the interior angles is 180 x (8 - 2) = 180 x 6 = 1,080º
Example
A regular polygon has an interior angle of 165.6º
How many sides does it have?
Answer
Exterior angle = 180 - interior angle = 180 - 165.6 = 14.4º
Number of sides = 360 ÷ exterior angle = 360 ÷ 14.4 = 25
So this regular polygon must have 25 sides.
Let's have a go at some questions now.
Question
/ 10Mr Shepherd
Do you want to skip questions and finish?
Hold up, it looks like there may be an issue with your spelling. Why not try it again?
You need to check your answer before you proceed. Are you sure you want to skip?
Teacher explanation