Regular polygon

Regular heptadecagon
A regular heptadecagon
Type	Regular polygon
Edges and vertices	17
Schläfli symbol	{17}
Coxeter diagram
Symmetry group	Dihedral (D17), order 2×17
Internal angle (degrees)	≈158.82°
Dual polygon	Self
Properties	Convex, cyclic, equilateral, isogonal, isotoxal

A regular polygon is a shape that can be drawn on a flat surface. It has sides that are all the same length, and its angles are all the same. In other words, a polygon which is both equilateral (which means all its sides have the same length) and equiangular (which means that all its angles are the same) is a regular polygon. It always has the same number of edges and points.

A polygon is also convex if there aren't any two points within it that can't be connected with a straight line, where the entire straight line is also in it. An example of a concave shape is a five-pointed star. It's concave because you can connect two of the points of a star with a straight line, and most of the straight line doesn't go through the star. If a five-pointed star is both equilateral and equiangular, it is also a regular polygon, but it isn't a convex one. All regular concave polygons are stars.