matthen:Unrolling these circles fills a triangle with base 2 π r and height r (where r is the radius
matthen:Unrolling these circles fills a triangle with base 2 π r and height r (where r is the radius of the filled disk). Such a triangle has area π r². This does not serve as a complete proof for why this is the area of a circle, but can give you some intuition for why it should be. [code] -- source link
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