The constructible regular 10-sided Polygon with Schläfli Symbol . The
Inradius , Circumradius , and Area can be computed directly from the formulas for a general
regular Polygon with side length and sides,
See also Decagram, Dodecagon, Trigonometry Values Pi/10, Undecagon
Dixon, R. Mathographics. New York: Dover, p. 18, 1991.