# Property of nonconvex polygons

How to prove that each non-convex polygon with no self-intersecting parts, has at least one interior angle which size is less then $180$ degrees.

-
In case of self-intersecting polygons, what is your definition of "interior angle"? – dtldarek Jan 25 '13 at 11:35

Hint: Consider the vertex with the largest $x$-coordinate.