The unconstructible regular seven-sided Polygon, illustrated above, has Schläfli Symbol .
Although the regular heptagon is not a Constructible Polygon, Dixon (1991) gives several close approximations. While the
Angle subtended by a side is
, Dixon gives constructions containing angles of
,
, and
.
Madachy (1979) illustrates how to construct a heptagon by folding and knotting a strip of paper.
See also Edmonds' Map, Trigonometry Values Pi/7
References
Courant, R. and Robbins, H. ``The Regular Heptagon.'' §3.3.4 in
What is Mathematics?: An Elementary Approach to Ideas and Methods, 2nd ed.
Oxford, England: Oxford University Press, pp. 138-139, 1996.
Dixon, R. Mathographics. New York: Dover, pp. 35-40, 1991.
Madachy, J. S. Madachy's Mathematical Recreations. New York: Dover, pp. 59-61, 1979.