1. Will return graded Unit 2 tests on Friday for reflection.
11/30: Classify a triangle by its sides and angles.
Do Now:
Have Out:
- Today’s Handouts
Begin your Warm-Up
Agenda:
Warm-Up & Check
Guided Notes
Guided Practice
Independent Practice
Closing & HW (…maybe…)
Homework
Handout (5 problems + 2 EC Problems)
Will return graded Unit 2 tests on Friday for reflection.
1st Period

2. Use the linear pair theorem to find the missing triangle angle measures:Z Y X
30°
90°
30°
90°
60°
180°
60°

3. Triangle Sum Theorem

4. Classify a triangle by its sides and angles.
We will learn to:
Classify a triangle by its sides and angles.

5. Graphic Organizer
Use the examples and non-examples at your table to fill out your graphic organizer.
Once you have finished, check with Mr. G BEFORE trying Examples 1 & 2

6. All 3 sides are congruent At least 2 congruent sides
No sides are congruent

7. All 3 angles are congruent
One right
angle
One obtuse
angle
All 3 angles are acute

8. How do we know it is obtuse?
Example 1: Classifying a Triangle by its Sides & Angles
Right Triangle
Isosceles Triangle
Obtuse Triangle
How do we know it is obtuse?

9. Example 2: Apply Properties of Isosceles & Equilateral Triangles
Check!
3x – 3 = 12
3(5) – 3 = 12
15 – 3 = 12
12 = 12

10. AB = BC 2x + 7 = 3x – 2 2x + 7 3x – 2 7 = x – 2 9 = x AB = 25 units
Example 2: Apply Properties of Isosceles & Equilateral Triangles
AB = BC
2x + 7 = 3x – 2
2x + 7
3x – 2
7 = x – 2
9 = x
64°
AB = 2x + 7
AB = 2(9) + 7
AB =
AB = 25 units

11. Example 2: Apply Properties of Isosceles & Equilateral Triangles
∠BAC ≅ ∠BCA
52°
2x + 7
3x – 2
m∠BCA = 64°
Triangle Sum Theorem
64°
64°
m∠BAC + m∠BCA + m∠ABC = 180°
______ + ______ + ________ = 180°
64°
64°
m∠BAC
m∠ABC = 52°

12. Triangle Sum Theorem 6x + 18 = 180° 6x = 162 x = 27
Example 3: Apply Triangle Sum Theorem to Classify Triangles
Triangle Sum Theorem
(2x + 10)°
m∠ABC + m∠ACB + m∠BAC = 180°
(x + 20)°
(3x - 12)°
______ + _______ + _______ = 180°
(x + 20)°
(3x – 12 )°
(2x + 10)°
6x + 18 = 180°
6x = 162
x = 27

13. Example 3: Apply Triangle Sum Theorem to Classify Triangles
m∠ABC = (x + 20)°
(2x + 10)°
m∠ABC = 47°
(x + 20)°
(3x - 12)°
m∠ACB = (3x – 12)°
m∠ACB = 69°
m∠BAC = (2x + 10)°
m∠BAC = 64°