POLYGONS

Polygons 

(FROM: https://www.mathsisfun.com/geometry/polygons.html)

A polygon is a closed plane figure with 3 or more straight sides and angles. Examples include triangles, quadrilaterals, pentagons, hexagons and so on.
Polygon comes from Greek. Poly- means "many" and -gon means "angle".

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) Types of Polygons Regular or Irregular A regular polygon has all angles equal and all sides equal, otherwise it is irregular Regular 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) Concave Convex 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 Complex More Examples Irregular Hexagon Concave Octagon Complex Polygon (a "star polygon", in this case a pentagram) Names of Polygons