2. Take a circle...

3. Divide it up into sectors

4. Colour the top semicircle green & the lower semicircle yellow

5. Pull the sectors apart

6. Arrange the green sectors in one line & the yellow sectors in another line

7. The sectors fit together like teeth..

11. Think about the lengths involved.. ? ?

12. The “vertical” one is easy... r ? It’s the radius!

13. The other is... r ? Half the circumference

14. Remember the formula for the circumference... r ?

15. So, half the circumference is... r ?

16. So, we have... r

17. But this shape is almost a rectangle... r So can you approximate its area?

18. The area is approximately r

19. Now, think... r What would happen if you cut the circle into smaller and smaller sectors?

20. It would become even more like a rectangle... r So this approximation for the area of the circle would be even more accurate...

21. So the area of a circle is...