A Vertex of a Simple Polygon is a principal Vertex if the diagonal intersects the boundary of only at and .

**References**

Meisters, G. H. ``Polygons Have Ears.'' *Amer. Math. Monthly* **82**, 648-751, 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.

© 1996-9

1999-05-26