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Ear


A principal vertex x_i of a simple polygon P is called an ear if the diagonal [x_(i-1),x_(i+1)] that bridges x_i lies entirely in P. Two ears x_i and x_j are said to overlap if

 int[x_(i-1),x_i,x_(i+1)] intersection int[x_(j-1),x_j,x_(j+1)]!=emptyset.

The two-ears theorem states that, except for triangles, every simple polygon has at least two nonoverlapping ears.


See also

Anthropomorphic Polygon, Mouth, Two-Ears Theorem

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References

Meisters, G. H. "Polygons Have Ears." Amer. Math. Monthly 82, 648-651, 1975.Meisters, G. H. "Principal Vertices, Exposed Points, and Ears." Amer. Math. Monthly 87, 284-285, 1980.Toussaint, G. "Anthropomorphic Polygons." Amer. Math. Monthly 98, 31-35, 1991.

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Ear

Cite this as:

Weisstein, Eric W. "Ear." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Ear.html

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