Bradley's Two-Triangles-to-One Dissection
This Demonstration shows Bradley's dissection of two triangles to one. Bradley used equilateral triangles and the dissection illustrated the Pythagorean theorem.
H. C. Bradley's solution to the problem appeared in the American Mathematical Monthly in 1930.
G. N. Frederickson, Dissections: Plane & Fancy, New York: Cambridge University Press, 1997 pp. 40–41.