Insert Lesson Title Here

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

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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