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 appearsEducação Superior::Ciências Exatas e da Terra::Matemática