Polygons
A polygon is a 2-dimensional shape. It is a closed plane figure made up of straight lines. The sides do not cross each other. Exactly two sides meet at every vertex.
A polygon is named by the number of its sides or angles. A triangle is a polygon with three sides. The prefix tri- means three. Prefixes are also used to name other polygons. A polygon with n sides is called n-gon.
A polygon is convex if no line that contains a side of the polygon contains a point in the interior of the polygon. A convex polygon has no angles pointing inwards. More precisely, no internal angles can be more than 180°.
A polygon that is not convex is called concave. If there are any internal angles greater than 180° then it is concave.
Read the full explanation below to learn more about polygons.
Practice: Answer the exercises below by naming polygons according to the number of sides and angles and finding the measures of interior and exterior angles of polygons.