Regular polytope impossible ("not constructible"). The simplest few regular polygons that are impossible to construct are the "n"-sided polygons with "n" equal to 7, 9, 11, 13, 14, 18, 19, 21... Constructibility in this sense refers only to ideal constructions with ideal tools. Of course reasonably accurate approximations can be constructed by a range of methods; while theoretically possible constructions may be impractical. Euclid's "Elements" gave what amount to ruler-and-compass constructions for the five Platonic solids. (See, for example, Euclid's Elements.) However, the merely practical question of how one might draw a straight line in space, even with a ruler, might lead
Regular polygon edges and faces in orthogonal projections "m"-cubes. In particular this is true for regular polygons with evenly many sides, in which case the parallelograms are all rhombi. The list gives the number of solutions for smaller polygons. The area "A" of a convex regular "n"-sided polygon having side "s", circumradius "R", apothem "a", and perimeter "p" is given by For regular polygons with side "s" = 1, circumradius "R" = 1, or apothem "a" = 1, this produces the following table: (Note that since formula_11 as formula_12, the area when formula_13 is tending to formula_14 as formula_15 grows large.) Of