regular star figures: {15/3}, {15/5}, {15/6}, the first being a compound of three pentagons, the second a compound of five equilateral triangles, and the third a compound of three pentagrams. The compound figure {15/3} can be loosely seen as the two-dimensional equivalent of the 3D compound of five tetrahedra. Isogonal pentadecagons Deeper truncations of the regular pentadecagon and pentadecagrams can produce isogonal (vertex-transitive) intermediate star polygon forms with equal spaced vertices and two edge lengths. Petrie polygons The regular pentadecagon is the Petrie polygon for some higher-dimensional polytopes, projected in a skew orthogonal projection: Uses A regular triangle, decagon, and pentadecagon can completely fill a plane vertex. However, due to the triangle's odd number of sides, the figures cannot alternate around the triangle, so the vertex cannot produce a semiregular tiling. See also Construction of the pentadecagon at given side length, calculation of the circumradius (German) Construction of the pentadecagon at given side length, exemplification: circumradius References External links Constructible polygons Polygons by the number of sides