1. Unit 4 – Lesson 1
Apply Triangle Sum Properties
And Angle Relationships

2. All sides are  Type of ∆ Definition Picture Equilateral Triangle
CLASSIFICATION BY SIDES

3. At least 2 sides  leg leg base Type of ∆ Definition Picture
Isosceles Triangle
At least 2 sides 
CLASSIFICATION BY SIDES
leg
leg
base

4. No sides are  Type of ∆ Definition Picture Scalene Triangle
CLASSIFICATION BY SIDES

5. All angles are  Type of ∆ Definition Picture Equiangular Triangle
CLASSIFICATION BY ANGLES

6. All angles are acute Type of ∆ Definition Picture Acute Triangle
CLASSIFICATION BY ANGLES

7. hypotenuse leg One right angle leg Type of ∆ Definition Picture
Right Triangle
hypotenuse
leg
One right angle
CLASSIFICATION BY ANGLES
leg

8. One obtuse angle and 2 acute angles
Type of ∆
Definition
Picture
Obtuse Triangle
One obtuse angle and 2 acute angles
CLASSIFICATION BY ANGLES

9. Interior Angles –
Angles inside a shape
Exterior Angles –
Angles outside a shape
Corollary –
Statement easily proved from another statement

10. b c a b c a
The sum of the measures of a triangle = _______
180°

11. If two triangles have two angles that are _______, 
If two triangles have two angles that are _______,
then the third angle is also ___________.  B E
80°
80°
40°
60°
40°
60° A C D F

12. The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles.
a + b = 180°
b + c + d = 180°
b + c + d = a + b
c + d = a

13. The acute angles of a right triangle are
______________.
complementary
a + c + 90 = 180° a
a + c = 90° c

14. Classify the triangle by its sides and angles.
scalene
right

15. Classify the triangle by its sides and angles.
equilateral
equiangular

16. Classify the triangle by its sides and angles.
isosceles
obtuse

17. 4. Find the value of x. Then classify the triangle by its angles.
2x + 3x + 55 = 180
5x + 55 = 180
75°
5x = 125
50°
x = 25°
acute

18. 4. Find the value of x. Then classify the triangle by its angles.
4x – 5 + 3x = 180
7x + 40 = 180
75°
7x = 140
65°
x = 20°
acute

19. 4. Find the value of x. Then classify the triangle by its angles.
2x x x + 1 = 180
52°
7x + 5 = 180
52°
76°
7x = 175
x = 25°
acute

20. 5. Find the measure of each exterior angle shown.
x + 80 = 3x – 22
-x x
80 = 2x – 22
102 = 2x
51° = x
3(51) – 22 =
131°

21. 5. Find the measure of each exterior angle shown.
2x – x = 6x – 7
x = 6x – 7
-x x
103 = 5x – 7
110 = 5x
22° = x
6(22) – 7 =
125°

22. 5. Find the measure of each exterior angle shown.
2x = 4x + 8
2x + 54 = 4x + 8
-2x x
54 = 2x + 8
46 = 2x
23° = x
4(23) + 8 =
100°

23. 6. Solve for the variables.
65°
25°
y = 180
y = 180
y = 25°

24. 6. Solve for the variables.
5y = 180
5y = 180
5y = 55
y = 11°
55°

25. 7. Find the measure of each missing angle.
120°
30°
60°
30°
60°
120°

26. HW Problem 4.1 # 26 Ans: 4.1 221 229 1-6, 14-18, 21-26 (FRONT PAGE)LT
Page #
Assignment
Due
4.1
221
229
1-6, 14-18, (FRONT PAGE)
32, 33, 35, 15, 16 (BACK PAGE)
4.1 # 26
Ans: