A principal vertex of a simple polygon is called a mouth if the diagonal is an extremal diagonal (i.e., the interior of lies in the exterior of ).
Mouth
See also
Anthropomorphic Polygon, Ear, One-Mouth TheoremExplore with Wolfram|Alpha
References
Toussaint, G. "Anthropomorphic Polygons." Amer. Math. Monthly 122, 31-35, 1991.Referenced on Wolfram|Alpha
MouthCite this as:
Weisstein, Eric W. "Mouth." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Mouth.html