Lesson

Let's review the properties of shapes to help us in this lesson.

Does a circle have straight or curved edges?

A

Straight

B

Curved

Worked Solution

Idea summary

An edge of a shape may be straight or curved. Squares, rectangles and triangles have straight edges. A circle has a curved edge.

Let's learn how to identify the features of circles.

Consider the circle below:

a

What is the diameter of the circle?

Worked Solution

b

What is the the radius of the circle?

Worked Solution

Idea summary

Circles have some important features, such as the radius, diameter and circumference. We can use these features, and others, to identify sectors, semi-circles, and quadrants.

The

**circumference**is the edge of the circle.The

**radius**is the distance from the centre of the circle to the circumference.The

**diameter**is the distance from one side of the circumference to the other, that passes through the centre.