Essential Question: What happened to Chapter 9?

Answer: We’ll get back to it

10-1: Naming PolygonsA polygon is named by the number of sides or

angles.Prefix Number

of SidesName of Polygon

Prefix Number of Sides

Name of Polygon

Tri- 3 Triangle Hepta- 7 Heptagon

Quadri- 4 Quadrilateral

Octa- 8 Octagon

Penta- 5 Pentagon Nona- 9 Nonagon

Hexa- 6 Hexagon Deca- 10 Decagon

10-1: Naming PolygonsWhen we studied quadrilaterals in Chapter 8,

we learned some rules that can be applied to all polygons.

P Q

R

ST

U

A vertex is thepoint of intersectionbetween two sides

A segment whose two endpoints are nonconsecutive vertices is called a diagonal

Consecutive vertices arethe two endpoints of anyside

Sides that share a vertexare called consecutivesides

10-1: Naming PolygonsAn equilateral polygon has all sides

congruent, and an equiangular polygon has all angles congruent. A regular polygon is both equilateral and equiangular.

Equilateral, but not equiangular

Equiangular, but not equilateral

Regular, bothequilateral andequiangular

10-1: Naming PolygonsIdentify polygon LMNOPQRS by its sides

OctagonDetermine whether the polygon

appears to be regular or not regular. If not regular,explain why.Not regular. L ≠ M

Name two nonconsecutive sidesLM & NO

L

MN

O

P

QR

S

10-1: Naming PolygonsYou can use the property of regular polygons (all

sides are the same length) to find the perimeter.P = (# of sides) x (length of each side)

ExampleFind the perimeter of a regular octagon whose sides

are 7.6 centimeters long P = (8)(7.6) = 60.8 cm

YOUR TURNFind the perimeter of a regular decagon whose sides

are 12 feet long. 120 ft

10-1: Naming PolygonsA polygon can also be classified as convex or

concave.If all the diagonals lie in the interior of a

polygon, then the polygon is convex.If any point of a diagonal lies outside the figure,

then the figure is concave. (“caved” in)

Convex polygon Concave polygon

10-1: Naming PolygonsAssignment

Worksheet 10-1