§8.4 Circumference of a circle

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

§8.4 Circumference of a circle

First you will see what the word 

circumference means.

perimeter and circumference, demonstrated by

the fridge and washing machine below:

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

circles!

Look at the picture to 

understand the meaning

of the words:

- radius and

- diameter    Learn how to pronounce it in the next slide!     

If we know 

the diameter, we can calculate the

circumference of the circle.

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!

Make task 23a in you Notebook.

To get the right measurements, you have to use your TEXTBOOK, p.56!

Solution :

Now make task 23b:

Solution 23b:

Do 23c now:

Solution 23c:

Make 23d now:

Solution 23d:

Make 23e now.

Solution:

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?

The following Movie uses     2 r  instead of d.

The radius fits two times in the diameter.

You know by now, that        

d = 2r

Get your Calculator on the table for the

following question!

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

2nd Task:

Give your answer exactly, so with               in it.

π

Solution. 2nd Task:

The number is exactly 3.14

π

1. true
2. not true

Solution:

Not true.

3.14   is an approximation for the number     

Watch the next slide for some more decimals of this number!

π

Homework

Do §8.4  and choose from these tasks:

-   24. t/m.  28.    or

-   24, 25, 27, C7 and C8