A polygonal diagonal is a line segment connecting two nonadjacent polygon vertices of a polygon. The number of ways a fixed convex -gon can be divided into triangles by nonintersecting diagonals is (with diagonals), where is a Catalan number. This is Euler's polygon division problem. Counting the number of regions determined by drawing the diagonals of a regular -gon is a more difficult problem, as is determining the number of -tuples of concurrent diagonals (Kok 1972).

The number of regions which the diagonals of a convex polygon divide its center if no three are concurrent in its interior is

The first few values are 0, 0, 1, 4, 11, 25, 50, 91, 154, 246, ... (Sloane's A006522).

Kok, J. Item 2 in Beeler, M.; Gosper, R. W.; and Schroeppel, R. HAKMEM. Cambridge, MA: MIT Artificial Intelligence Laboratory, Memo AIM-239, p. 3, Feb. 1972. http://www.inwap.com/pdp10/hbaker/hakmem/geometry.html#item2.

Sloane, N. J. A. Sequence A006522/M3413 in "The On-Line Encyclopedia of Integer Sequences."

CITE THIS AS:

Weisstein, Eric W. "Polygon Diagonal." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/PolygonDiagonal.html