Decomposition into Isosceles Triangles with Angles That Are Multiples of Pi/4
Figures such as a square, an octagon, or an octagram can be dissected into isosceles triangles where all three angles are multiples of . Such triangles have the same role as iso-penta triangles for five-fold symmetry. The figures in this Demonstration are not always decomposed into triangles; sometimes squares and rhombuses, which can be divided along a diagonal into two such triangles, are left whole.
 G. N. Frederickson, Dissections: Plane & Fancy, New York: Cambridge University Press, 2002 p. 212. www.cs.purdue.edu/homes/gnf/book.html.