Download 1 OBJECTIVE:ааYou will learn to use the Angle Sum Theorem

Warm up: Classify each triangle by its angles and sides.
1. 2. 60°
45°
60°
45°
60°
3. Triangle ABC has angles that measure 110, 50 and 20. Classify the triangle by its angles.
4. Triangle RST has sides that measure 3 feet, 4 feet and 5 feet. Classify the triangle by it sides.
5. Triangle KLM is an equilateral triangle in which KL = 3x ­ 2,
LM = x + 8 and KM = 2x +3. Find the measure of each side.
Dec 7­9:29 AM
OBJECTIVE: You will learn to use the Angle Sum Theorem.
Section 5­2
__________________
Angle Sum Theorem
The sum of the measures of the angles of a triangle is 180.
Example 1: Find m T in RST.
R
54°
67°
S
T
Dec 7­9:29 AM
1
Example 2: Find the value of each variable in DCE.
E
B
y°
C
85° x°
55°
A
D
Dec 7­9:29 AM
Theorem 5 ­ 2 ­­The acute angles of a right triangle are complementary.
Example 3: Find m A and m B in right triangle ABC.
C
A
2x°
3x°
B
Dec 7­9:29 AM
2
equiangular triangle ­­
Theorem 5­3 ­­The measure of each angle of an equiangular
triangle is 60.
Dec 7­9:30 AM
Guided Practice:
1. Choose the numbers that are not measures of the three
angles of a triangle.
a. 10, 20, 150
b. 30, 60, 90
c. 40, 70, 80
d. 45, 55, 80
2. Is it possible to have two obtuse angles in a triangle? Why or why not?
Dec 7­9:30 AM
3
Find the value of each variable.
3. 4.
68°
30°
x°
58°
y°
y°
Dec 7­9:31 AM
5.
63°
a°
b°
50°
6. The measures of the angles of a triangle are 2x, 3x and 4x.
Find the measure of each angle.
Dec 7­9:31 AM
4
Do you have any Vocab questions?
OBJECTIVE:
HOMEWORK: p. 196 ­ 197
# 8 ­ 20, 22 ­ 30 even
Dec 7­9:31 AM
5