1. Insert Lesson Title Here
Course 2
8-5
Classifying Polygons
Insert Lesson Title Here
Learn to identify and name polygons.

2. Polygon - 8-8 Angles in Polygons
Course 2
8-8
Angles in Polygons
Polygon -
A closed figure with 3 or more straight sides that do not cross.

3. 8-5 Classifying Polygons
Course 2
8-5
Classifying Polygons
Determine whether each figure is a polygon. If it is not, explain why not.

4. Regular Polygon - 8-8 Angles in Polygons
Course 2
8-8
Angles in Polygons
Regular Polygon -
A polygon with congruent sides and angles.

5. 8-5 Classifying Polygons
Course 2
8-5
Classifying Polygons
Determine whether each figure is a regular polygon. If it is not, explain why not.

6. Diagonal - 8-8 Angles in Polygons
Course 2
8-8
Angles in Polygons
Diagonal -
A straight line that joins two non-adjacent vertices of a polygon.

7. Course 2
8-8
Angles in Polygons
Learn to find the measures of angles in polygons.

8. Course 2
8-8
Angles in Polygons
Take the paper triangle on your desk and name the corners 1, 2, and 3.
Carefully tear off two of the corners.
Rotate them so the straight edges meet at the vertex and point in the same direction as the un-torn corner.
You should find that they formed a straight angle.
This suggests that the sum of the measures of the angles in a triangle is 180°.

9. 8-8 Angles in Polygons Angles of a Triangle
Course 2
8-8
Angles in Polygons
Angles of a Triangle
The sum of the measures of the angles in a triangle is 180°.
m1 + m2 + m3 = 180° 2 1 3

10. Remember this from 6th grade? How many degrees are in a quadrilateral?
Course 2
8-8
Angles in Polygons
Remember this from 6th grade?
How many degrees are in a quadrilateral?
Angles of a Quadrilateral
The sum of the measures of the angles in a quadrilateral is 360°.
m1 + m2 + m3 + m4 = 360° 1 2 4 3

11. Course 2
8-8
Angles in Polygons
Let’s Triangulate!

12. 8-8 Angles in Polygons Number of sides
Course 2
8-8
Angles in Polygons
Number of sides
Skip this slide. For teacher use only
Name of figure
(Number of triangles) x 180o = Total interior degrees

13. Course 2
8-8
Angles in Polygons
3 sides
Triangle
(1)180o = 180o

14. Course 2
8-8
Angles in Polygons
4 sides
Quadrilateral
(2)180o = 360o

15. Course 2
8-8
Angles in Polygons
5 sides
Pentagon
(3)180o = 540o

16. Course 2
8-8
Angles in Polygons
6 sides
Hexagon
(4)180o = 720o

17. Course 2
8-8
Angles in Polygons
8 sides
Octagon
(6)180o = 1080o

18. Noticing any pattern yet???
Course 2
8-8
Angles in Polygons
(# of triangles)180 = total interior degrees
3 sides
4 sides
5 sides
6 sides
8 sides
50 sides
n sides
(1)180° = 180 °
Noticing any pattern yet???
(2)180° = 360 °
(3)180° = 540 °
(4)180° = 720 °
(6)180° = 1080 °
(48)180° = 8640 °
(n - 2)180°

19. 8-8 Angles in Polygons Find the measure of the unknown angles. 1. 2.
Course 2
8-8
Angles in Polygons
Find the measure of the unknown angles.

20. Course 2
8-8
Angles in Polygons
Find the unknown angle measure in the quadrilaterals.

21. Course 2
8-8
Angles in Polygons
Take out yesterday’s notes:

22. Classifying Triangles
Course 2
8-6
Classifying Triangles
Classify each triangle according to its sides and angles. 3 C.
___ congruent sides
___ _______ angles 3
acute
This is an________ _______ triangle.
equilateral
acute D.
___ congruent sides No
obtuse
___ _____ angle 1
This is a _______ _____ triangle.
scalene
obtuse

23. Insert Lesson Title Here
Course 2
8-6
Classifying Triangles
Insert Lesson Title Here
Classify each triangle according to its sides and angles. 2
___ congruent sides E.
___ _______ angles 1
obtuse
This is an________ _______ triangle.
isosceles
obtuse F.
___ congruent sides 2 1
right
___ _____ angle
This is a _______ _____ triangle.
isosceles
right

24. Classifying Triangles
Course 2
8-6
Classifying Triangles
Identify the different types of triangles in the figure, and determine how many of each there are.
Type
How many
Name
Scalene 2
ABD,
BCD
Isosceles 2
ACE,
ABC
Right 2
ABD,
BCD
Obtuse 1
ACE
Acute 1
ABC

25. Math Humor
What did the girl have to use to get her enormous collection of CD-Roms to her friend’s house?
a CD-ROMbus!!!

26. Insert Lesson Title Here
Course 2
8-8
Angles in Polygons
Insert Lesson Title Here
Lesson Quiz
Find the measure of the unknown angle for
each of the following.
1. a triangle with angle measures of 66° and 77°
37°
2. a right triangle with one angle measure of 36°
54°
3. an quadrilateral with angle measures of 144°, 84°, and 48°.
84°
4. Divide a six-sided polygon into triangles to
find the sum of its interior angles
720°