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# Understanding Pi

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by

## Mr Mattock

on 18 September 2016

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#### Transcript of Understanding Pi

Understanding Circles
Starter
Find the perimeter of this shape:

Why would it be difficult to find the circumference of this shape?
Activity
Take each of the circular or cylindrical objects, measure the diameter of the circle, and then use the paper strips to measure the circumference of the circle.

Divide the circumference by the diameter.

What do you notice?
Example
Geogebra demonstration

https://www.geogebra.org/m/NdCdwY6F

L.O. - Understand the important relationships that appear between circles.
5 cm
9 cm
Starter
Find the perimeter of this shape:

Why would it be difficult to find the circumference of this shape?
5 cm
9 cm
28 cm
It is curved
The ratio of the circumference and diameter of any circle is always pi (greek letter ).

This is important because it means that instead of trying to measure the curved edge of a circle, we can measure the straight distance across the circle and
calculate
the circumference of the circle.
Circles and Pi
Interesting Pi
Although pi is an irrational number, it has lots of very regular forms. For example:

Use the Ipads to find some other interesting expressions for pi.
Activities
Activity

Key
Information

pi = 4(1 - + - + - + .....)
1
3
1
5
1
7
1
9
1
11
Full transcript