Area of the Circle - Alternative

Here's an elementary way to find the area of a circle although I'm sure many of you are already familiar with it.
Slice up the circle into 4 parts and stack them up as follows.



Now do the same except that the number of slices this time is 8.



Now increase the number of slices to 16.


Do you see something familiar. The figure we are stacking is starting to resemble a rectangle.
Finally if we make an infinite number of slices and stack them up we will find a rectangle of 
area = $\pi r\times r=\pi r^2$

Source:Take it to the limit by Steven Strogatz

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