Download Study Guide and Intervention Classifying Triangles

NAME
DATE
4-1
PERIOD
Study Guide and Intervention
Classifying Triangles
Classify Triangles by Angles
One way to classify a triangle is by the measures
of its angles.
•
If all three of the angles of a triangle are acute angles, then the triangle is an acute triangle.
•
If all three angles of an acute triangle are congruent, then the triangle is an equiangular triangle.
• If one of the angles of a triangle is an obtuse angle, then the triangle is an obtuse triangle.
If one of the angles of a triangle is a right angle, then the triangle is a right triangle.
Example
a.
Lesson 4-1
•
Classify each triangle.
A
60°
B
C
All three angles are congruent, so all three angles have measure 60°.
The triangle is an equiangular triangle.
E
b.
120°
35°
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
D
25°
F
The triangle has one angle that is obtuse. It is an obtuse triangle.
c.
G
90°
H
60°
30°
J
The triangle has one right angle. It is a right triangle.
Exercises
Classify each triangle as acute, equiangular, obtuse, or right.
2. N
1. K
30°
67°
L
23°
Q
60°
M
R
obtuse
5.
T
65° 65°
acute
60°
60°
B
6.
60°
45°
V
X
S
equiangular
W
50°
Chapter 4
3.
P
right
U
O
120°
90°
4.
30°
90°
45°
right
Y
F
28°
92°
D
obtuse
5
Glencoe Geometry
NAME
DATE
4-1
PERIOD
Study Guide and Intervention
(continued)
Classifying Triangles
Classify Triangles by Sides You can classify a triangle by the number of congruent
sides. Equal numbers of hash marks indicate congruent sides.
•
If all three sides of a triangle are congruent, then the triangle is an equilateral triangle.
•
If at least two sides of a triangle are congruent, then the triangle is an isosceles triangle.
Equilateral triangles can also be considered isosceles.
•
If no two sides of a triangle are congruent, then the triangle is a scalene triangle.
Example
a.
Classify each triangle.
b.
H
c.
N
T
23
L
R
J
Two sides are congruent.
The triangle is an
isosceles triangle.
X
P
All three sides are
congruent. The triangle
is an equilateral triangle.
12
V
15
The triangle has no pair
of congruent sides. It is
a scalene triangle.
Exercises
Classify each triangle as equilateral, isosceles, or scalene.
2.
A
2
G
18
1
C
√⎯3
K
scalene
4.
18
Q
I
5. B
C
O
19
scalene
32x
8x
W
17
12
18
equilateral
S
M
3.
G
x
6. D
A
x
32x
E
x
F
U
isosceles
isosceles
7. ALGEBRA Find x and the length of each
side if RST is an equilateral triangle.
equilateral
8. ALGEBRA Find y and the length of
each side if ABC is isosceles with
AB = BC.
#
3
2x + 2
4
5x - 4
3x
4y
5
"
2; 6
Chapter 4
3y + 2
3y
$
2; AB = 8; BC = 8, AC = 6
6
Glencoe Geometry
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
1.