tridecagon
triskaidecagon

The regular tridecagon is used as the shape of the Czech 20 korun coin.

An approximate construction of a regular tridecagon using straightedge and compass is shown here.

The regular tridecagon has Dih symmetry, order 26.

These 4 symmetries can be seen in 4 distinct symmetries on the tridecagon.

The regular tridecagon is the Petrie polygon 12-simplex:

As 13 is a Pierpont prime but not a Fermat prime, the regular tridecagon cannot be constructed using a compass and straightedge.

Hired workmen and troops assembled the fort, using 9 foot high and 5 foot thick adobe walls to construct the irregular tridecagon structure.

Examples are the trisection of any angle in three equal parts, the doubling of the cube, and the construction of a regular heptagon, nonagon, or tridecagon (polygons with 7, 9, or 13 sides).

The following is an animation from a neusis construction of a regular tridecagon with radius of circumcircle according to Andrew M. Gleason, based on the angle trisection by means of the Tomahawk (light blue).

When only an angle trisector is permitted, there is a complete description of all regular polygons which can be constructed, including above mentioned regular heptagon, triskaidecagon (13-gon) and enneadecagon (19-gon).