1. Lesson 19 Polygons
Kalyani David

2. Objective
1. Define polygon 2. Identify and describe polygons by the number of sides and angles 3. Explain the difference between regular and irregular polygons

3. What is a Polygon????
Any ideas?
Write down what you think it is for

4. A polygon is…
a closed figure with three or more sides.

5. A polygon is a closed figure with 3 or more sides
(all straight lines, no curves).

6. Check your work Polygon Not a polygon Not a polygon polygon polygon

7. Check your work Polygon polygon polygon Not a polygon Not a polygon

8. Where do we see Polygons in our everyday Environment ?
Essential Question
Where do we see Polygons in our everyday Environment ?

9. Classifying Polygons

10. A triangle has three sides.1 3 2

11. A Quadrilateral has four sides.4 3 1 2

12. A pentagon has five sides.1 5 2 4 3

13. Hexagon
A hexagon has six sides.

14. Heptagon
A heptagon has seven sides.
heptagon

15. Octagon
An octagon has eight sides.

16. 8 sided Polygon = Octagon
Hint: “oct”opus – 8 legs

17. Number of Sides
Name 3
Triangle 4
Quadrilateral 5
Pentagon 6
Hexagon 7
Heptagon 8
Octagon 9
Nonagon 10
Decagon 11
Hendecagon 12
Dodecagon

18. Q: What do we call a polygon with more than 12 sides?
Classifying Polygons by
number of Sides
Q: What do we call a polygon with more than 12 sides?
A : An ‘n’-gon where ‘n’ is the number of sides
Ex: a 20 sided polygon is a 20-gon

19. Let’s Review:
The triangle is the smallest polygon. It only has three sides.
A pentagon has five sides.
A hexagon has six sides.
A heptagon has seven sides.
An octagon has eight sides.

20. Match these. Triangle eight sides Heptagon three sides
Octagon seven sides

21. Match some more. Pentagon four sides Hexagon five sides
Square six sides

22. Key Question:
A triangle is the smallest polygon because it has three sides. Can you have a two-sided polygon? Why or why not?
Two lines don’t close to make a shape. They make an angle. 1 2

23. Practice set and Written Practice from your Text Page:123
Home Work
Practice set and Written Practice from your Text Page:123