Enneagram

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In geometry, an enneagram is a nine-pointed geometric figure. The term derives from two ancient Greek words: ennea (nine) and gramma (something written).

Enneagrams shown as sequential stellations

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[edit] Regular enneagrams

A regular enneagram (a nine-sided star polygon), is constructed using the same points as the regular enneagon but connected in fixed steps. It has two forms, represented by a Schläfli symbol as {9/2} and {9/4}, connecting every second and every fourth points respectively.

There is also a star figure, {9/3} or 3{3}, made from the regular enneagon points but connected as a compound of three equilateral triangles.[1][2] This last is sometimes also called a nonagram. This geometrical figure should not be confused with the logic puzzles called nonograms.


Complete graph K9

Enneagon {9/1}

Star polygon {9/2}

Star figure 3{3}

Star polygon {9/4}

[edit] Other Enneagrams


The final stellation of the icosahedron has 2-isogonal enneagram faces. It is a {9/4} wound star polyhedron, but the vertices are not equally spaced.

The Enneagram of Personality and Fourth Way Enneagram use an irregular enneagram, constructed from a triangle and an irregular hexagram.

The Bahá'í nine-pointed star

[edit] Use in popular culture

[edit] See also

[edit] References

  1. ^ Grünbaum, B. and G. C. Shephard; Tilings and Patterns, New York: W. H. Freeman & Co., (1987), ISBN 0-7167-1193-1.
  2. ^ Grünbaum, B.; Polyhedra with Hollow Faces, Proc of NATO-ASI Conference on Polytopes ... etc. (Toronto 1993), ed T. Bisztriczky et al, Kluwer Academic (1994) pp. 43-70.

[edit] External links

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