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Henri Picciotto's Math Education Page

Henri Picciotto

The circumference (perimeter) of a circle is given by the formula C = 2π*r*, where *r* is the radius, and π = 3.141592653... This applet is one way to understand how this leads to the formula for the area of a circle.

We start by dividing a circle into 12 sectors.

- Click on the "rearrange" check box to rearrange the sectors.
- Use the slider to divide the circle into more and more smaller and smaller sectors
- The smaller the sectors, the more the rearranged sectors approximate a rectangle.
- When the sectors are very small, what are the dimensions of the rectangle?
- What is the area of the circle?