In this activity, we will be calculating the area of sectors of a circle.
You will need a scientific calculator.
A sector is a portion or a part of a circle.
To find the area of a circle we square the radius and multiply it by pi
What is pi (π) in numbers?
Pi is an infinite number, and you can use a function on your calculator to input the number.
Here is the start of it 3.14159265359...
We write it like this in short:
Area of a circle = π r2
To find a sector we are finding a portion of this formula.
Let's look at a question.
Example
Find the area of a sector of a circle with radius 6 cm.
Angle at the centre is 45o
Give your answer to 1 decimal place.
Answer
Area = π r2 x 45 ÷ 360
This is because we want 45/360ths of a full circle area.
= π × 62 x 45/360
= π × 36 x 45 ÷ 360
= 14.1 cm2 (to 1 dp)
Remember, in this activity, you need to use a scientific calculator to calculate pi correctly.
You can access one of these online if you do not have one.
Let's do some questions like this!