Some polygons are concave and some are convex .
A convex polygon is a polygon such that no line containing a side of the polygon contains a point in the interior of the polygon. A polygon that is not convex is concave . Examples of concave and convex polygons. Names of some polygons go to top of page Definition of a Regular Polygon - A regular polygon is a convex polygon with all sides congruent and all angles congruent. Using the formula you substitute 3 for n and solve.