A polygon is a plane figure. A polygon is a closed region. A polygon is formed by three or more segments as its sides. Each side of a polygon intersects only one segment at each of its endpoints. poli + gonus “many angled” What is a polygon?
Polygon or Not a Polygon? Polygon
Polygon or Not a Polygon? Not Polygon because sides are not segments.
Polygon or Not a Polygon? Not Polygon because sides are intersecting not just at the endpoints.
Polygon or Not a Polygon? Polygon
Polygon or Not a Polygon? Not Polygon because sides are intersecting not just at the endpoints.
Polygon or Not a Polygon? Polygon
Polygon or Not a Polygon? Not Polygon because sides are intersecting more than one other side at its endpoint.
Regions in a Polygon
Parts of a Polygon sides consecutive sides included angle nonconsecutive sides interior angles / vertex angles consecutive angles included side nonconsecutive angles exterior angles diagonals
ALL POLYGONS
ALL POLYGONS???
ALL POLYGONS!
How can these polygons be divided into two groups?
Convex Polygons Concave Polygons
Polygon Convexity A polygonal region is convex if any segment joining any two points of the polygon is part of the interior region. If a polygon is not convex, then its is concave .
Convex or Concave? Convex
Convex or Concave? Concave because a segment connecting points on the polygon that will lie in the exterior can be drawn.
Convex or Concave? Convex
Convex or Concave? Concave because a segment connecting points on the polygon that will lie in the exterior can be drawn.
Convex or Concave? Concave because a segment connecting points on the polygon that will lie in the exterior can be drawn.
Convex or Concave? Convex
Convex or Concave? Concave because a segment connecting points on the polygon that will lie in the exterior can be drawn.
Polygons are named by writing their consecutive vertices in order, such as ABCD or CDAB for the polygon above. We cannot name the polygon as DBAC. Naming Polygons B A C D
Connecting to Prior Knowledge Think of words beginning with the prefixes tri-, quad-, pent-, and oct - . Examples: triathlon, quadriplegic, pentameter, and octopus. Meanings? (words and prefixes)
Polygons can be named by their number of sides. Number of Sides Name of Polygon 3 triangle 4 quadrilateral 5 pentagon 6 hexagon 7 heptagon 8 octagon 9 nonagon 10 decagon 11 undecagon 12 dodecagon