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Geometry Coach
geometry coach lesson plans
Common Core Standard  6.G.1 ,  6.G.3, 7.G.6
Convex Polygon
Concave Polygon
Related sites...

Naming polygons game  This could be a great way to review the polygon names. The polygon game shows a shape and then asks you questions about the name or number of sides.

Naming Polygons Tips and directions for naming polygons
convex polygon
concave polygon
When you draw a line through a Concave polygon it touches the concave polygon in more that two places,but with a Convex polygon the line only touches it in two places
video tutorial naming polygons
Concave polygons do have 
internal angles greater than  180°




Convex polygons do not have any
internal angles greater than than ​180°



1. Regular Polygons have equal length sides ( congruent sides)








2. Regular Polygons have equal length angles ( congruent angles)










3. Because the measure of each central angle is congruent in regular polygons, you can find the measure of the central  angle by dividing the number of sides into 360◦ 
360 ÷ N (Number of sides) = Measure​ of the Central Angle of a regular polygon








Names of Polygons

convex polygon
concave polygon
regular polygon quadrilateral
regular polygon
regular polygon square triangle/properties and names of polygons
central angle polygon
In this example the central angle equals

360/5 sides = 72 degrees
You may also enjoy ....

Parallelograms

2D Polygons



Names of Polygon Shapes

Name

Number of Sides

Interior Angle Measure

Central Angle Measure

360/number of sides

Triangle

3

60°

120°

Quadrilateral

4

90°

90°

Pentagon

5

108°

72°

Hexagon

6

120°

60°

Heptagon or Septagon

7

128.5°

51.4°

Octagon

8

135°

45°

Nonagon or Enneagon

9

140°

40°

Decagon

10

144°

36°

Hendecagon or Undecagon

11

147.2°

32.72°

Dodecagon

12

150

30°

Triskaidecagon

13

152.3°

27.69°

Tetrakaidecagon

14

154.2°

25.71°

Pentadecagon

15

156°

24°

Hexakaidecagon

16

157.5°

22.5°

Heptadecagon

17

158.82°

21.17°

Octakaidecagon

18

160°

20°

Enneadecagon

19

161.05°

18.94°

Icosagon

20

162°

18°

Triacontagon

30

168°

12°

Tetracontagon

40

171°

Pentacontagon

50

172.8°

7.2°

Hexacontagon

60

174°

Heptacontagon

70

174.85°

5.14°

Octacontagon

80

175.5°

4.5°

Enneacontagon

90

176°

Hectagon

100

176.4°

3.6°

Chiliagon

1000

176.64°

.36°

Myriagon

10,000

179.96°

.036°

n-gon

n

(n-2) × 180° / n

 

You can make names using

Number of sides

 

For example

40 Tetraconta

 

+1 henagon

+2 digon

+3 trigon

+4 tetragon

+ 5 pentagon

+6 hexagon

+7 heptagon

+ 8 octagon

+9 enneagon

 

 

Tetracontakaihenagon =41 sides

Tetracontakaidigon =42 sides

Tetracontakaitrigon = 43 sides

 

 

Central Angle
plus "Kai" for "and"
An easier and acceptable method of naming many sided polygons is as follows: 13 sided = 13-gon  17 sided =17-gon
Many of the shapes in Geometry are polygons. What is a polygon? A polygon is a two dimensional shape that has straight lines. A polygon can have anywhere between three and an unlimited number of sides. All of the lines of a polygon connect which means there is not an opening. Each polygon is named according to it's number of sides. Here are some examples of polygons.