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
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