Pythagoras Proof 3

A third proof of the Pythagorean Theorem. This one is a bit more mysterious: how is the quadrilateral constructed? It is due to Dudeney (1917) (citation from the book Proofs Without Words by Roger B. Nelsen).

Print 4 of the quadrilaterals and one each of the others. The triangle is just for reference; it is not used in the proof, but can be helpful in verifying that a,b,c are all honestly sides of a right triangle.