Circle Formulae 1

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Circle Formulae 1
The circumference of a circle Tandi
Clausen-May
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The circumference
of a circle
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First we need ? (pi)
What is ? ? Is it a number?

• Is it..
• 3.14159265358979323846264338
• 327950288419716939937510582097
• 494459230781640628620899862803
• 482534211706798214808651328230
• 66470938446095505822172535..?

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?

• Well not exactly.
• ? is a ratio.

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Pi is the number of times you must travel
straight across the circle to go the same
distance as all the way round the circle.
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Once across
twice across
three times across
and a bit further!
So ? is a bit more than 3.
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How can we be sure that ? is a bit more than 3?
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For a regular hexagon, the distance all the way
round is exactly 3 times the distance straight
across the middle.
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And all the way round the circle is a little
bit more than all the way round the hexagon.
So all the way round the circle is a little bit
more than 3 times straight across the middle.
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Circumference ? Diameter
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Summary
Circumference
? Diameter
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Circle Formulae 2
Now watch
The area of a circle
Tandi Clausen-May