Number of sides Type of Polygon

3 Triangle

4 Quadrilateral

5 Pentagon

6 Hexagon

7 Heptagon

Number of sides Type of Polygon

8 Octagon

9 Nonagon

10 Decagon

12 Dodecagon

n n-gon

Convex if no line that contains a side of the polygon contains a point in the interior of the polygon.

Concave or non-convex if a line does contain a side of the polygon containing a point on the interior of the polygon.

See how it doesn’t go on theInside-- convex

See how this crossesa point on the inside?Concave.

Remember: Equiangular & equilateral

Decide whether the following polygons are regular.

Equilateral, but not equiangular, so it is NOT a regular polygon.

Heptagon is equilateral, but not equiangular, so it is NOT a regular polygon.

Pentagon is equilateral and equiangular, so it is a regular polygon.

Students will analyze and determine angle measures in polygons.

Why? So you can describe a baseball park, as seen in Examples 28 & 29.

Mastery is 80% or better on 5-minute checks and practice problems.

Page 510-512

#’s 3-31 all

State whether the figure is a polygon. If it is not, explain why.

Not D – has a side that isn’t a segment – it’s an arc.

Not E– because two of the sides intersect only one other side.

Not F because some of its sides intersect more than two sides/

F

E

D

CBA

Figures A, B, and C are polygons.

Identify the polygon and state whether it is convex or concave.

A polygon is EQUILATERALIf all of its sides are congruent.A polygon is EQUIANGULARif all of its interior angles are congruent. A polygon is REGULAR if it isequilateral and equiangular.