Name
Date
LESSON
Class
Practice C
8-4 Triangles
Find the value of each variable.
1.
62°
4.
2.
x°
3.
44°
n°
x°
w°
w°
118°
t°
t°
5.
6.
59°
t°
2x °
m°
x°
64°
7. The measure of the second angle in a triangle is four more than
the measure of the first angle and the measure of the third angle
is eight more than twice the measure of the first angle. Find the
measure of each angle.
Describe each statement as always, sometimes, or never true.
8. An obtuse triangle is a scalene triangle.
9. A scalene triangle is an isosceles triangle.
10. A right triangle is an isosceles triangle.
11. In the figure, R
T
is a diagonal of
rectangle QRST. Find the length of QT
.
Q
R
25 ft
T
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
31
24 ft
S
Holt Mathematics
Practice B
8-4 Triangles
Practice A
8-4 Triangles
LESSON
LESSON
1. Find x° in the right
triangle.
Identify each triangle by its angles and sides.
1.
2.
70°
3.
64°
126°
27°
40°
70°
x°
27°
26°
acute, isosceles
41°
5. Find y° in the right
triangle.
x°
110°
40°
x°
n°
50°
65°
8. Find y° in the right
triangle.
y°
70°
80°
35°
30°
42°
78°
66°
53°
J
13 in.
12 in.
8 in.
A
n° 85°
42°
10. In the figure, M is the midpoint of JK
and L
M
is
perpendicular to JK
. Find the length of LM
.
B
10 in.
9. Find n° in the scalene
triangle.
x° x°
37°
65°
25°
10. In the figure, D is the midpoint of AC
and B
D
is
perpendicular to AC
. Find the length of B
C
.
38°
8. Find x° in the isosceles
triangle.
48°
55°
48°
52°
t°
100°
m°
t°
49°
68°
7. Find t° in the scalene
triangle.
9. Find m° in the obtuse
triangle.
74°
w°
63°
47°
6. Find t° in the right
triangle.
37°
40°
30°
59°
m°
5. Find w° in the acute
triangle.
108°
r°
y°
55° 60°
46°
91°
4. Find n° in the obtuse
triangle.
6. Find r° in the obtuse
triangle.
3. Find m° in the acute
triangle.
y°
obtuse, isosceles
Find each angle measure.
7. Find x° in the acute
triangle.
43°
49°
right, scalene
4. Find x° in the acute
triangle.
2. Find y° in the obtuse
triangle.
10 in.
M
L
C
D
12 in.
K
11. The second angle in a triangle is three times as large as the
first. The third angle is one third as large as the second angle.
Find the angle measures. Draw a possible picture of the
triangle.
36°
1
108°
11. The second angle in a triangle is one third as
large as the first. The third angle is two thirds
as large as the first angle. Find the angle
measures. Draw a possible picture of
the triangle.
36°
sample answer
36°, 108°, 36°
sample answer 90° 60°
30°, 60°, 90°
29
Copyright © by Holt, Rinehart and Winston.
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Holt Mathematics
LESSON
Find the value of each variable.
Acute Triangle
2.
x°
62°
3.
44°
n°
x°
59°
4.
w°
118°
31°
6.
59°
Obtuse Triangle
t°
C
c°
In the diagram: mA mB mC 180°
x°
64°
1 obtuse angle
Triangle Sum Theorem: The sum of the measures
of the three interior angles of any triangle is 180°.
2x °
m°
1 right angle
3 acute angles
60°
5.
Right Triangle
t°
t°
46°
w°
Holt Mathematics
Review for Mastery
8-4 Triangles
LESSON
1.
30
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Practice C
8-4 Triangles
30°°
A
a°
b°
B
a° b° c° 180°
57°
30°
Complete to find the measure of the unknown angle.
7. The measure of the second angle in a triangle is four more than
the measure of the first angle and the measure of the third angle
is eight more than twice the measure of the first angle. Find the
measure of each angle.
1.
2.
C
x°
K
32°
A 58°
42°
first 42°; second 46°; third 92°
B
J
x ° 90°
L
Describe each statement as always, sometimes, or never true.
mA mB mC 180°
8. An obtuse triangle is a scalene triangle.
sometimes
58°
9. A scalene triangle is an isosceles triangle.
42°
100°
never
180°
x° x° 180°
x° x° 10. A right triangle is an isosceles triangle.
sometimes
3.
11. In the figure, R
T
is a diagonal of
rectangle QRST. Find the length of QT
.
Q
T
24 ft
S
35°
31
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Holt Mathematics
180°
180°
58°
W
122°
U
x°
20°
V
Z
mU mV mW 180°
x° 35° 35° 180°
x° 20° 122° 180°
x° 70° 180°
x° 142° 180°
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
93
mX mY mZ 180°
x° Copyright © by Holt, Rinehart and Winston.
All rights reserved.
122°
4.
35°
90°
x° X
x°
Y
32°
80°
R
25 ft
7 ft
mJ mK mL 180°
x° 110°
x° 32
38°
Holt Mathematics
Holt Mathematics