Polygon

Is It a polygon?

Polygons are 2-dimensional shapes. They are made of straight lines, and the shape is "closed" (all the lines connect up).

Polygon 
(straight sides)

Not a Polygon 
(has a curve)

Not a Polygon 
(open, not closed)

 Polygon comes from Greek. Poly- means "many" and -gon means "angle".

Types of Polygons

Regular or Irregular

A regular polygon has all angles equal and all sides equal, otherwise it is irregular

Regular

Irregular

Irregular

Concave or Convex

A convex polygon has no angles pointing inwards. More precisely, no internal angle can be more than 180°. If any internal angle is greater than 180° then the polygon is concave. (Think: concave has a "cave" in it)

Convex

Concave

Simple or Complex

A simple polygon has only one boundary, and it doesn't cross over itself. A complex polygon intersects itself! Many rules about polygons don't work when it is complex.

Simple Polygon (this one's a Pentagon)

Simple Polygon
(this one's a Pentagon)

Complex Polygon
(also a Pentagon)

More Examples

Irregular Hexagon 

Concave Octagon

Complex Polygon

Names of Polygons

Polygon Song

Exercise

Qustion 1-10 

GAME

Reference

https://www.mathsisfun.com/geometry/polygons.html

https://www.youtube.com/watch?v=TbR_rakilds

https://www.mathplayground.com/matching_shapes.html