1. Polygons
Where has Polly gone?

2. Polygon
A closed figure formed by joining three or more segments in a plane at their endpoints, with each line segment joining exactly 2 others.
Each line segment is called a side of the polygon.
This polygon has 8 sides.

3. Circle the figures that are polygons:

4. Why are these NOT polygons?
A. Open side
B. Curved side
C. Vertex has more than 2 segments that meet
D. Curved side B C D

5. Vertex and diagonal A vertex is where 2 sides meet.
A diagonal joins two nonconsecutive vertices.
Name the vertices and the diagonal in this polygon:
Vertices: A,B,C,D,E,F
Diagonal: CE

6. List all the diagonals in this polygon:DB DA EC EB AC E B C D

7. Polygons are named by the number of sides.

8. Name these polygons: A E B C F D A. triangle B. Quadrilateral
C. Pentagon
D. Hexagon
E. Octagon
F. Dodecagon E B C F D

9. Polygons with all sides and angles equal are regular polygons
Polygons with all sides and angles equal are regular polygons. Circle the regular polygons:

10. Polygons are named by naming consecutive vertices in order.
Circle all the correct names for this polygon:
pentagon ABCDE
pentagon AEDCB
pentagon ACDBE
pentagon DCBAE
pentagon BDCAE
pentagon BAEDC

11. What is the sum of the angle measures in a triangle?
Please draw a triangle on a piece of scratch paper. It can be any size or shape, just be sure it is a triangle.

12. Now, tear off the three angles of the triangle
Now, tear off the three angles of the triangle. Position the angles side-by-side on your desk. What shape do they make?
a straight line!
Draw the angles side-by-side on your paper like this ↑

13. What is the measure of a straight line?
180

14. The sum of the angles of any triangle is 180°
Find the measure of the missing angle:
ے1 = (90 +35)
ے1 = (125)
ے1 = 55°
35°
90° ے1

15. The sum of the angles of any triangle is 180°
Find the measure of the missing angle:
ے2 = ( )
ے2 = (130)
ے2 = 50° ے2
65°
65°

16. Find x: 3x - 4 + 5x + 10 + 6x + 6 = 180 14x + 12 = 180 -12 -12
14x = 168
x = 12

17. What is the sum of the angle measures in a polygon?
We can divide the polygon into triangles, then multiply the number of triangles by 180°
How many triangles make up this quadrilateral? 2
What is the sum of the angles of this quadrilateral?
2 x 180° = 360°

18. What is the sum of the angles in this hexagon?
720°

19. What is the sum of the angles in this pentagon?
3 x 180° =
540°

20. Do you HAVE to draw the triangles to find out how many of them there are in a polygon?
NO!
4 sides, 5 sides, sides,
2 triangles triangles triangles
n sides,
n-2 triangles!

21. What is the sum of the measures of the angles of these polygons?
180(6-2) 180(8-2) 180(10-2)
= 180(4) =180(6) = 180(8)
= 720° = 1080° =1440°

22. Find the missing angle measure in this polygon:
180(5-2)
= 180(3)
= 540°
540° = X
540 = X
116° = X

23. Find the missing angle measure in this polygon:
180(9-2)
= 180(7)
= 1260°
1260° = X
1260 = X
121° = X

24. raise your achievement
practice will
raise your achievement
The End