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Course 2
8-5 Classifying Polygons
Learn to identify and name polygons.
Course 2
8-8 Angles in Polygons
Polygon -
A closed figure with 3 or more straight sides that do not cross.
Determine whether each figure is a polygon. If it is not, explain why not.
Course 2
8-5 Classifying Polygons
Course 2
8-8 Angles in Polygons
Regular Polygon -
A polygon with congruent sides and angles.
Determine whether each figure is a regular polygon. If it is not, explain why not.
Course 2
8-5 Classifying Polygons
Course 2
8-8 Angles in Polygons
Diagonal -
A straight line that joins two non-adjacent vertices of a polygon.
Learn to find the measures of angles in polygons.
Course 2
8-8 Angles in Polygons
Course 2
8-8 Angles in Polygons
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°.
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.
Course 2
8-8 Angles in Polygons
Angles of a Triangle
The sum of the measures of the angles in a triangle is 180°.
m1 + m2 + m3 = 180°
1 3
2
Course 2
8-8 Angles in Polygons
Angles of a Quadrilateral
The sum of the measures of the angles in a quadrilateral is 360°.
m1 + m2 + m3 + m4 = 360°
1
2
4
3
Remember this from 6th grade?
How many degrees are in a quadrilateral?
Course 2
8-8 Angles in Polygons
Let’s
Triangulat
e!
Course 2
8-8 Angles in Polygons
Name of figure
(Number of triangles) x 180o = Total interior degrees
Number of sides
Skip this slide. For teacher use only
Course 2
8-8 Angles in Polygons
3 sides
Triangle
(1)180o = 180o
Course 2
8-8 Angles in Polygons
4 sides
Quadrilateral
(2)180o = 360o
Course 2
8-8 Angles in Polygons
5 sides
Pentagon
(3)180o = 540o
Course 2
8-8 Angles in Polygons
6 sides
Hexagon
(4)180o = 720o
Course 2
8-8 Angles in Polygons
8 sides
Octagon
(6)180o = 1080o
Course 2
8-8 Angles in Polygons
3 sides
4 sides
5 sides
6 sides
8 sides
50 sides
n sides
(# of triangles)180 = total interior degrees
(1)180° = 180 °
(2)180° = 360 °
(3)180° = 540 °
(4)180° = 720 °
(6)180° = 1080 °
(48)180° = 8640 °
(n - 2)180°
Noticing any
pattern yet???
Find the measure of the unknown angles.
Course 2
8-8 Angles in Polygons
1. 2.
Find the unknown angle measure in the quadrilaterals.
Course 2
8-8 Angles in Polygons
4. 5.
Take out yesterday’s notes:
Course 2
8-8 Angles in Polygons
Classify each triangle according to its sides and angles.
Course 2
8-6 Classifying Triangles
C. ___ congruent sides
___ _______ angles
This is an________ _______ triangle.
D. ___ congruent sides
___ _____ angle
This is a _______ _____ triangle.
acute
3
3
equilateral acute
No
1 obtuse
scalene obtuse
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Classify each triangle according to its sides and angles.
E.
F.
Course 2
8-6 Classifying Triangles
___ congruent sides
___ _______ angles
This is an________ _______ triangle.
___ congruent sides
___ _____ angle
This is a _______ _____ triangle.
obtuse
2
1
isosceles obtuse
2
1 right
isosceles right
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
Right
Obtuse
Acute
ACE, ABC
ABD, BCD
ACE
ABC
2
2
1
1
Course 2
8-6 Classifying Triangles
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!!!
Lesson Quiz
54°
37°
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84°
720°
Course 2
8-8 Angles in Polygons
Find the measure of the unknown angle for each of the following.
1. a triangle with angle measures of 66° and 77°
2. a right triangle with one angle measure of 36°
3. an quadrilateral with angle measures of 144°, 84°, and 48°.
4. Divide a six-sided polygon into triangles to find the sum of its interior angles
