The Circle

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The Circle
Main Parts of a Circle
Formula for Circumference
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Starter Questions
Level 2

7cm
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Main part of a Circle
Learning Intention We are learning to identify
the main parts of a circle.

• Success Criteria
• Understand the terms
• circumference, diameter and radius.
• 2. Identify them on a circle.
• 3. Calculate the circumference using formula.

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Main part of a Circle
Main parts of the circle
O
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Main part of a Circle
2cm
10cm
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Main part of a Circle
Your turn Exercise 1 Chapter 19 Page 228
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Starter Questions
Level 2

5cm
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Stars In Your Eyes
Level 2
Today Matthew we are going to be

Archimedes of Syracuse
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History of Circles
75 years old
Level 2
The Greek mathematician Archimedes of Syracuse (28
7- 212 BC) who flourished in Sicily is generally
considered to be the greatest mathematician of
ancient times. He is credited with determining
the relationship between the diameter and the
circumference of a circle. This was first
recorded by Archimedes in the book Measurement
of a Circle (225 BC). In this investigation we
are going to attempt to follow Archimedes
steps and arrive at the equation for determining
the circumference for any given circle.
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22931 years old
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Parts of the Circle
Level 2
O
O centre of circle
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Circle Investigation
Level 2

• Construct a table shown below to enable us
• to record our results.

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Investigation of the Circle
Level 2
Our Investigation
To find a relationship between the diameter and
circumference of a given circle.
Question ?
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How can we measure the diameter and circumference
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Measuring the Diameter of a circle
Level 2
O
The diameter is the largest distance between one
side of a circle to the other passing through
the centre O.
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Measuring the Circumference of a circle
Level 2
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Measuring the Circumference of a circle
Level 2
Roll along an even surface
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One complete rotation equals the length of the
circumference
Be careful to avoid slip!
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Circle Investigation
Level 2
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Circle Investigation
Level 2

• Using your results write down, in your own
  words,
• an approximate relationship between the
• circumference and diameter for a given circle.

Circumference approximately equals three and bit
diameters Actual value is 3.14 which we write as
?
Pronounced Pi
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Circle Investigation
Level 2
Chapter 19 Exercise 2 Page 229 Q2
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