8-6 Classifying Triangles Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes.
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8-6 Classifying Triangles
Warm UpWarm Up
Lesson PresentationLesson Presentation
Problem of the DayProblem of the Day
Lesson QuizzesLesson Quizzes
8-6 Classifying Triangles
Warm Up1. What is the name of a six-sided figure?
2. What is the definition of an acute angle?
3. The measure of one of two supplementary angles is 32°. What is the measure of the other angle?
hexagon
an angle that measures less than 90°
148°
8-6 Classifying Triangles
Problem of the Day
Use 6 congruent line segments to form 4 equilateral triangles. (Hint: Use toothpicks or other objects to model the segments.)
Place the segments so they form a pyramid.
8-6 Classifying Triangles
Learn to classify triangles by their side lengths and angle measures.
8-6 Classifying Triangles
Vocabulary
scalene triangleisosceles triangleequilateral triangleacute triangleobtuse triangleright triangle
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides.
Triangles classified by sides
A scalene trianglehas no congruent sides.
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides.
Triangles classified by sides
An isosceles trianglehas at least 2 congruent sides
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides.
Triangles classified by sides
In an equilateral triangle, all of the sides are congruent.
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles.
Triangles classified by angles
In an acute triangle, all of the angles are acute.
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles.
Triangles classified by angles
An obtuse triangle hasone obtuse angle.
8-6 Classifying Triangles
One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles.
Triangles classified by angles
A right triangle has one right angle.
8-6 Classifying Triangles
Classify each triangle according to its sides and angles.
Additional Example 1: Classifying Triangles
A. Two congruent sidesacute Three acute angles
This is an isosceles acute triangle.
B. No congruent sidesright One right angle
This is a scalene right triangle.
isosceles
scalene
8-6 Classifying Triangles
Classify each triangle according to its sides and angles.
Additional Example 1: Classifying Triangles
C. Three congruent sides
acute Three acute angles
This is an equilateral acute triangle.
D. No congruent sides
right One right angle
This is a scalene right triangle.
equilateral
scalene
8-6 Classifying Triangles
Check It Out: Example 1
Classify each triangle according to its sides and angles.
A. Two congruent sidesacute One obtuse angle
This is an isosceles acute triangle.
B. Two congruent sides
right One right angle
This is an isosceles right triangle.
isosceles
isosceles
8-6 Classifying Triangles
Check It Out: Example 1
Classify each triangle according to its sides and angles.
C. No congruent sidesobtuse One angle exceeding 90°
This is a scalene obtuse triangle.
D. No congruent sides
obtuse One angle exceeding 90°
This is a scalene obtuse triangle.
scalene
scalene
8-6 Classifying Triangles
Identify the different types of triangles in the figure, and determine how many of each there are.
Additional Example 2: Identifying Triangles
NameHow manyType
Scalene 2 ABD, BCD
Isosceles
Right
Obtuse
Acute
ACE, ABC
ABD, BCD
ACE
ABC
2
2
1
1
8-6 Classifying Triangles
Check It Out: Example 2
A
BC
D
EF
G
H
I J
Identify the different types of triangles in the figure, and determine how many of each there are.
Isosceles
Obtuse
Acute
5
2
4
NameHow manyType
DJA, JDG
HJI, BCD
DFE
DJA, ADG
JDG, JHI,
BCD, DEF
8-6 Classifying Triangles
Standard Lesson Quiz
Lesson Quizzes
Lesson Quiz for Student Response Systems
8-6 Classifying Triangles
Lesson Quiz
Classify each triangle according to its sides and angles.
1. 7 ft, 8 ft, 12 ft
2. 45°, 90°, 45°
3. 12, 9, 12
4. 120°, 20°, 40°
5. Identify the different types of triangles in the figure and determine how many of each there are.
right
scalene
isosceles
obtuse
1 isosceles acute triangle, 1 equilateral triangle, 1 scalene right triangle
8-6 Classifying Triangles
1. Classify the triangle according to its sides.9 ft, 16 ft, 9 ft
A. equilateral
B. isosceles
C. scalene
D. right
Lesson Quiz for Student Response Systems
8-6 Classifying Triangles
2. Classify the triangle according to its sides. 5 in., 8 in., 12 in.
A. equilateral
B. isosceles
C. scalene
D. right
Lesson Quiz for Student Response Systems
8-6 Classifying Triangles
3. Classify the triangle according to its angles. 45°, 105°, 30°
A. acute
B. obtuse
C. right
D. equilateral
Lesson Quiz for Student Response Systems
8-6 Classifying Triangles
4. Classify the triangle according to its angles. 27°, 90°, 63°
A. acute
B. obtuse
C. right
D. equilateral
Lesson Quiz for Student Response Systems
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