Download Notes - Godley ISD

Similar Triangles
You will need two different colored
highlighters
Similar figures have the same shape but not necessarily the
same size.
When naming similar figures, list the letters of the
corresponding vertices in the same order. ∆ABC ~ ∆DEF.
Two figures are similar if
• The measures of their corresponding angles are
equal.
• The ratios of the lengths of the corresponding
sides are proportional.
Matching sides of two or more polygons are called
corresponding sides, and matching angles are called
corresponding angles.
Corresponding
angles
E
B
82◦
82◦
A
43◦
55◦
D
C
43◦
Corresponding sides
55◦
F
Determine if the shapes are proportional. Do not rely on a visual
EX1)
A
4 in
G
C
28 in
16 in
10 in
7 in
F
H
40 in
1. Highlight
corresponding sides
2. Set up proportions
3. Simplify
B
Small
Large
4 in
16 in
1 in
4 in
=
=
10 in
40 in
1 in
4 in
=
=
7 in
28 in
1 in
4 in
EX2) City officials want to know the height of a traffic light.
26
18
= 39
h
Set up a proportion.
Simplify.
h ft
18 ft
26 ft
39 ft
13 = 39
9
h
351 ÷13
h = 27
Solve proportions.
EX3) Draw and Label a similar triangle LMN to triangle ABC with a scale
factor of 1/4.
A
16 X 1/4 = 4
8 X 1/4 = 2
16
Draw in the hypotenuse
L
B
C
8
N
M
EX4) Determine the ratios of corresponding sides between triangles.
LM
AB
=
4
1
=
16
MN
4
BC
=
2
=
8
1
4
EX5) Determine the ratios of corresponding sides within triangles.
AB
BC
=
16
8
=
2
1
LM
MN
=
4
2
=
2
1
Essential Question
Name two attributes that determine if figures are
similar?
Date ____________
Similar Triangles
You will need two different colored
highlighters
Similar figures have the __________ shape but not necessarily
the same size.
When naming similar figures, list the letters of the
corresponding vertices in the _______________________.
∆ABC ~ ∆DEF.
Two figures are similar if
• The measures of their corresponding angles are
__________.
• The ratios of the lengths of the corresponding
sides are _________________.
Matching sides of two or more polygons are called
corresponding sides, and matching angles are called
corresponding angles.
Corresponding
angles
E
B
82◦
82◦
A
43◦
55◦
D
C
43◦
Corresponding sides
55◦
F
EX1) Determine if the shapes are proportional. Do not rely on a visual
A
G
C
1.
H
F
3.
B
Small
Large
2.
=
=
=
=
EX2)
City officials want to know the height of a traffic light.
EX3) Draw and Label a similar triangle LMN to triangle ABC with a scale
factor of
.
A
B
C
EX4) Determine the ratios of corresponding sides between triangles.
EX5) Determine the ratios of corresponding sides within triangles.
Essential Question
Name two attributes that determine if figures are
similar?