The unconstructible regular Polygon with nine sides and Schläfli Symbol . It is sometimes called an Enneagon.

Although the regular nonagon 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 nonagon by folding and knotting a strip of paper.

**References**

Dixon, R. *Mathographics.* New York: Dover, pp. 40-44, 1991.

Madachy, J. S. *Madachy's Mathematical Recreations.* New York: Dover, pp. 60-61, 1979.

© 1996-9

1999-05-25