WOLFRAM|DEMONSTRATIONS PROJECT

An Example of the Bolyai-Gerwien Theorem

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rotate
elongate
show axes of rotation
This conceptual design can be used to demonstrate the Bolyai–Gerwien theorem in the case of triangles and rectangles. A triangle is cut into four pieces that can be rotated to form a rectangle. (Henry Dudeney published this as a plane rearrangement puzzle in 1902.)