Area of a Circle - Wedge Demo 1

We know that the area of a circle is: A=πr². But a real proof of this is hard.
Here we show a demonstration of this fact by cutting the circle into wedges and placing half of the wedges face up and half face down. As the number of wedges increases, we see that they cover a rectangle with A=base•height = ½ of circumference •radius = ½(2πr)•r = πr²

This is a Java Applet created using GeoGebra from - it looks like you don't have Java installed, please go to

Why is the base of the rectangle half of the circumference of the circle?
Why did we label the x-axis with units of π and the y-axis with units of numbers?

Created with GeoGebra – Shared by LFS