Polygon and their angles

1. DEMO PRESENTATION

2. Can you guess our lesson’s title ?
 According to the given video

3. Polygons and their angles
The word polygon means
“many angles”
A two dimensional object
A closed figure

4. More about Polygons
• Made up of three or more
straight line segments.
• There are exactly two sides
that meet at a vertex.
• The sides do not cross each
other.
Polygons

5. State some geometric figures are there in
• A) Home .
• B) Street .
• C) Work .
• D) Sports .

6. Examples of Polygons
Polygons

7. These are not Polygons

8. Keywords
Side: One of the line
segments that make up a
polygon.
Vertex: Point where two
sides meet.
Polygons

9. Vertex
Side

10. • Interior angle: An angle
formed by two adjacent
sides inside the polygon.
• Exterior angle: An angle
formed by two adjacent
sides outside the polygon.

11. Interior angle
Exterior angle
Polygons

12. Let us recapitulate
Interior angle
Diagonal
Vertex
Side
Exterior angle

13. • Regular Polygon: a polygon
where all the angles are equal
and all of the sides are the
same length. They are both
equilateral and equiangular.
Polygons

14. Task
• Draw 2 different triangles .
• Measure its all angles .
• Calculate the sum .
• What do you deduce ?

15. Examples of Regular Polygons
Polygons

16. INTERIOR ANGLES
OF A POLYGON
Polygons

17. Let us find the connection
between the number of sides,
number of diagonals and the
number of triangles of a polygon.

18. Hand out activity
Complete the following worksheet

19. Quadrilateral
Pentagon
180
o 180
o
180o 180o
180o
2 x 180o = 360o
3
4 sides
5 sides
… x 180
o
= …
o
Hexagon6 sides
180o 180o
180o
180o
… x 180o = …o
4
Heptagon/Septagon… sides
180o
180o
180o
180o
180o
…. x 180o = …….o
…
2
1 diagonal
2 diagonals
…. diagonals
…. diagonalsPolygons

20. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0

21. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Polygons

22. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Pentagon 5 2 3 3 x180
0
= 540
0
540
0
/5
= 108
0

23. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Pentagon 5 2 3 3 x180
0
= 540
0
540
0
/5
= 108
0
Hexagon 6 3 4 4 x180
0
= 720
0
720
0
/6
= 120
0

24. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Pentagon 5 2 3 3 x180
0
= 540
0
540
0
/5
= 108
0
Hexagon 6 3 4 4 x180
0
= 720
0
720
0
/6
= 120
0
Heptagon 7 4 5 5 x180
0
= 900
0
900
0
/7
= 128.3
0

25. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Pentagon 5 2 3 3 x180
0
= 540
0
540
0
/5
= 108
0
Hexagon 6 3 4 4 x180
0
= 720
0
720
0
/6
= 120
0
Heptagon 7 4 5 5 x180
0
= 900
0
900
0
/7
= 128.3
0
“n” sided
polygon
n Association
with no. of
sides
Association
with no. of
sides
Association
with no. of
triangles
Association
with sum of
interior
angles

26. Regular
Polygon
No. of
sides
No. of
diagonals
No. of Sum of the
interior
angles
Each
interior
angle
Triangle 3 0 1 180
0
180
0
/3
= 60
0
Quadrilateral 4 1 2 2 x180
0
= 360
0
360
0
/4
= 90
0
Pentagon 5 2 3 3 x180
0
= 540
0
540
0
/5
= 108
0
Hexagon 6 3 4 4 x180
0
= 720
0
720
0
/6
= 120
0
Heptagon 7 4 5 5 x180
0
= 900
0
900
0
/7
= 128.3
0
“n” sided
polygon
n n - 3 n - 2 (n - 2)
x180
0
(n - 2)
x180
0
/ n
Polygons

27. Credentials and references
1-Some materials of this PowerPoint was kindly donated to
www.worldofteaching.com
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submitted by teachers. This a free site. Please visit and I hope it
will help in your teaching
2- Video was found on : www.youtube.com .
3- Provided lesson regard international standards NCTM
https://www.nctm.org/