Polygons and Angles
Concept

Concave Polygon

A concave polygon is a polygon in which at least one line containing a side of the polygon also contains points in the interior of the polygon. Alternatively, a polygon is concave if one or more interior angles have a measure greater than Note that only polygons with four or more sides can be concave.
Concave polygons and lines containing the sides
Some features can be listed about concave polygons.
  • At least one vertex of the polygon points inwards.
  • Some of the diagonals may lie partly or entirely outside the polygon.
  • There are points inside the polygon for which the segment joining them is not fully contained in the polygon.
  • Concave polygons are always irregular.
Concave polygon with a diagonal lying outside it.
When a polygon is not concave, it is said to be convex.
Exercises