Welcome Geometry!
• Take out your whiteboard and whiteboard pens.
• Take out a piece of paper and title it:
– 4.1: Classifying Triangles
Transformation Test Results
Overall, I am very proud of each and everyone of you for putting your
best effort into the test.
1st Period
o Average 29.6 out of 31
o 95%
3rd Period
o
o
Average 24.6 out of 31
79%
4th Period
o
o
•
•
Average 26.7 out of 31
86%
You will get the tests back sometime this week. I still have
students who need to take it!
The scores are on Infinite Campus
Do Now!:Whiteboards
Classify each angle as acute, obtuse, or right.
1.
2.
3.
4. What are the possible degrees of an acute, obtuse,
right, and straight angle.
4.1: Classifying Triangles
Learning Objective
SWBAT classify triangles by their angle measures and
side lengths.
Tonight's homework:
Pg. 219 #1-11 And Classifying Triangles Worksheet
4-1 Classifying Triangles
Todays topic is all about classifying triangles, meaning
what category do they fall under.
We can classify triangles two ways:
1. By their angle measures.
2. By their side lengths.
4-1 Classifying Triangles
Lets recall how to label the sides and angles.
C
A
B
AB, BC, and AC are the sides of
A, B, C are the triangle's vertices.
ABC.
4-1 Classifying Triangles
Triangle Classification By Angle Measures
Acute Triangle
Three acute angles
4-1 Classifying Triangles
Triangle Classification By Angle Measures
Equiangular Triangle
Three congruent acute angles
4-1 Classifying Triangles
Triangle Classification By Angle Measures
Right Triangle
One right angle
4-1 Classifying Triangles
Triangle Classification By Angle Measures
Obtuse Triangle
One obtuse angle
4-1 Classifying Triangles
Example 1
By Angle
Measures
Classify all of the triangles in the figure
by their
angle
measures.
Whiteboards
Classify
ABD by its angle measures.
Classifying by Side Lengths
Triangle Classification By Side Lengths
Equilateral Triangle
Three congruent sides
4-1 Classifying Triangles
Triangle Classification By Side Lengths
Isosceles Triangle
At least two congruent sides
4-1 Classifying Triangles
Triangle Classification By Side Lengths
Scalene Triangle
No congruent sides
4-1 Classifying Triangles
NOTE:
By Angle Measures
When you look at a figure, you cannot assume
segments or angles are congruent based on
appearance. They must be marked as congruent using
tick or arc marks.
4-1 Classifying Triangles
Example 2
By Angle Measures
Classify all of the triangles in the figure by their side
lengths.
Whiteboards
1. Classify ACD by its side lengths.
2. Classify ADB by its side lengths.
3. Classify ACB by its side lengths.
4-1 Classifying Triangles
Example 3
Find the side lengths of
By Angle Measures
JKL.
Whiteboards
Find the side lengths of equilateral
FGH.
Whiteboards
Classify each triangle by its angles and sides.
1. MNQ
2. NQP
3. MNP
4-1 Classifying Triangles
On the bottom of your notes write down Closure
questions:
By Angle Measures
If you do not do them, you will lose participation
points.
Do the questions all by yourself. I expect to hear no
one talking.
Closure Questions
1. Classify each triangle in the figure by its sides.
2. Find the side lengths of the triangle.
Homework:
• Pg. 219 #1-11 And Classifying Triangles
Worksheet ( from the front table)