WOLFRAM|DEMONSTRATIONS PROJECT

Mamikon's Proof of the Pythagorean Theorem

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sweep
0.772832
inner radius
In the left diagram, line segment
A
is tangent to the inner circle of an annular ring. Using the "sweep" slider, you can sweep
A
through the entire area of the ring. Simultaneously, on the right, that same line segment,
A
—now with one end pegged to a single point—sweeps out the same area, but forms a circular disk. Surprisingly, a new proof of the Pythagorean theorem discovered by Mamikon Mnatsakanian in 1959 (first published in 1981) dramatically appears.