CIRCLE

Discovering the Formula of the Area of a Circle

Plan : Work with a small group to make a display showing relationship between the area of  
circle with the area of the other geometric puzzle from the circle.

Act :

1.Draw a circle with 20 cm in diameter

2.Divide circle into 16 equal sectors

3.Cut each part of the circle

4.Arrange each part into a puzzle of geometric figure

A. Draw a circle with 20 cm in diameter

B. Divide circle into 16 equal sectors

C. Cut each part of the circle

D. Arrange each part into a puzzle of geometric figure

Solve the Problem

Below, some questions to help Solve the problem

1. From the geometric puzzle, what is the formula of area of it ? a.t

2. Can you use this formula to find out the formula of area of a circle ? yes

3. Can you explain and prove that the area of geometric puzzle is equal to the area of the 

             circle ?

Answer

 

Area Circle = Area Parallelogram

Area Circle = a.t

Area Circle = (1/4 .π .2r) (2r)

Area Circle = 1/4 .π .2r . 2r

Area Circle = 1/4 .π .4r²

Area Circle = π.r²

Conclution

If we discover the area, we will know that the area of 

parallelogram and the circle are same