CK-12 Geometry-Concepts

1.12. Polygon Classification http://www.ck12.org

Example C

Which of the figures below isnota polygon?

Cis a three-dimensional shape, so it does not lie within one plane, so it is not a polygon.

Watch this video for help with the Examples above.

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/52583

CK-12 Foundation: Chapter1PolygonClassificationB

Vocabulary

Apolygonis any closed planar figure that is made entirely of line segments that intersect at their endpoints. The

segments are called thesidesof the polygons, and the points where the segments intersect are calledvertices.

Polygons can be eitherconvexorconcave. A concave polygon has a section that “points inward” toward the middle

of the shape.Diagonalsare line segments that connect the vertices of a convex polygon that are not sides.

Guided Practice

Name the three polygons below by their number of sides and if it is convex or concave.

Answers:

A. This shape has six sides and concave, so it is a concave hexagon.

B. This shape has five sides and is convex, so it is a convex pentagon.

C. This shape has ten sides and is convex, so it is a convex decagon.