§8.4 Circumference of a circle

§8.4 Circumference of a circle
First you will see what the word 
circumference means.
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§8.4 Circumference of a circle
First you will see what the word 
circumference means.

Slide 1 - Diapositive

perimeter and circumference, demonstrated by
the fridge and washing machine below:


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both words mean 'omtrek' but circumference is only used for
circles!

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Look at the picture to 
understand the meaning
of the words:
- radius and
- diameter    Learn how to pronounce it in the next slide!     

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If we know 
the diameter, we can calculate the
circumference of the circle.

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How can there ever be a Formula for the 
Circumference of a circle?
The reason for this is that there is a fixed relationship 
between 
-   the Diameter.  and 
-   the Circumference of a Circle!
-   let's find this out with the following exercise!

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Make task 23a in you Notebook.
To get the right measurements, you have to use your TEXTBOOK, p.56!
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Solution :

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Now make task 23b:
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Solution 23b:

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Do 23c now:
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Solution 23c:

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Make 23d now:
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Solution 23d:

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Make 23e now.
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Solution:

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The next slide...
presents you with the GENERAL CONCLUSION from all the work you just did.
In other words: what do we know now about the relation between
the Circumference and the Diameter of a Circle?

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The following Movie uses     2 r  instead of d.
The radius fits two times in the diameter.
You know by now, that        
d = 2r

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Slide 23 - Vidéo

Get your Calculator on the table for the
following question!

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All think about this task!     
 Try to give your answer exactly, so with           in your answer,
and without, as an approximation.
Remember: your calculator has a button for the value of              !
π
π
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2nd Task:
Give your answer exactly, so with               in it.
π
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Solution. 2nd Task:

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The number is exactly 3.14
π
A
true
B
not true

Slide 30 - Quiz

Solution:
Not true.
3.14   is an approximation for the number     
Watch the next slide for some more decimals of this number!
π

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Homework
Do §8.4  and choose from these tasks:
-   24. t/m.  28.    or
-   24, 25, 27, C7 and C8

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