Where does pi r squared come from? Beautiful demonstration

Area of Circles Geogebra applet designed by Anthony Or, Education Bureau, Hong Kong

Here is something a bit special. It’s an amazing Geogebra applet that shows where the formula for the area of a circle comes from. I’ve had pupils cutting circles into sectors before to perform the same proof, but this interactive applet it first class in showing the concept in a visually stunning way and quickly. Top stuff!

Click here to launch the Area of a Circle applet.

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1 Response

  1. Trever Reeh says:

    Tried to do this in the classroom, big backfire. I tried using string for the outside for them to figure out what pi was and for them to explore and figure out what the sine and cosine wave looked like…. not pretty.

    I would try it again with another class, but this applet would definitely come in handy!

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