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 |
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) |
|
 |
Complex Polygon
(also a Pentagon) |
More Examples
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| Irregular Hexagon |
 |
| Concave Octagon |
 |
| Complex Polygon |
Names of Polygons
Polygon Song
Exercise
Reference
https://www.mathsisfun.com/geometry/polygons.html
https://www.youtube.com/watch?v=TbR_rakilds
https://www.mathplayground.com/matching_shapes.html
