Download Lesson 4.2 Properties of Special Triangles notes

4.2 Properties of Special Triangles
isosceles triangle – a triangle with at least _____ congruent sides. If a triangle has exactly _____
congruent sides, they are called the _______ and the angle between them is called the
___________________. The side opposite the vertex angle is called the ________. The nonvertex
angles are called the _______________.
vertex
angle
legs
base angles
base
Isosceles Triangle Conjecture
If a triangle is isosceles, then its base angles are ______________.
Converse of the Isosceles Triangle Conjecture
If a triangle has two congruent angles, then it is an _____________ triangle.
Geometry Lesson 4.2: Properties of Special Triangles
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Example 1: Find the missing measures.
A
D
mB = ______
48
F
mC = ______
mE = ______
mF = ______
B
C
mD = ______
E
H
42
mG = ______
mI = ______
G
I
Example 2: Find mA, mB, mD, and EC.
A
7 cm
E
42
96
C
7 cm
3 cm
D
B
mA = _______
mB = _______
mD = _______
EC = _______
Geometry Lesson 4.2: Properties of Special Triangles
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Example 3: The perimeter of ΔDOG is 142cm. Find mD and DO.
D
mD = _______
DO = _________
45 cm
72
O
G
Example 4: Solve for x.
x = ______
(2x - 20)
(6x)
Geometry Lesson 4.2: Properties of Special Triangles
x = ______
(3x - 60)
(5x)
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Example 5: Find x and y.
x
y
108
x = ______
x
y
102
y= ______
x = ______
y= ______
Example 6: Solve for x.
(5x + 5) m
30 m
(3x + 4) m
x = ______
40 m
x = ______
(4x + 9) m
25 m
x = ______
Geometry Lesson 4.2: Properties of Special Triangles
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Example 7: Find the measure of each lettered angle.
c
r
b
e
k
d
g
63
n
61
p
a
31
f
m
a = ______
b = ______
c = ______
d = ______
f = ______
g = ______
h = ______
k = ______
n = ______
p = ______
r = ______
h
e = _____
m = _____
Homework: pp. 206 – 207 => 1 - 8
Geometry Lesson 4.2: Properties of Special Triangles
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