Hendecagon of a regular hendecagon is still impossible even with the usage of an angle trisector. It can, however, be constructed via neusis construction and also via two-fold origami. Close approximations to the regular hendecagon can be constructed, however. For instance, the ancient Greek mathematicians approximated the side length of a hendecagon inscribed in a unit circle as being 14/25 units long. The following construction description is given by T. Drummond from 1800: On a unit circle: The "regular hendecagon" has Dih symmetry, order 22. Since 11 is a prime number there is one subgroup with dihedral symmetry: Dih, and 2
Hendecagon cyclic group symmetries: Z, and Z. These 4 symmetries can be seen in 4 distinct symmetries on the hendecagon. John Conway labels these by a letter and group order. Full symmetry of the regular form is r22 and no symmetry is labeled a1. The dihedral symmetries are divided depending on whether they pass through vertices (d for diagonal) or edges (p for perpendiculars), and i when reflection lines path through both edges and vertices. Cyclic symmetries in the middle column are labeled as g for their central gyration orders. Each subgroup symmetry allows one or more degrees of freedom for