# Course 2 Lesson 10

```Lesson 10-6
Pages 440-443
Similar
Figures
What you will learn!
How to determine whether
figures are similar and find
a missing length in a pair
of similar figures.
Similar figures
Indirect measurement
What you really need to know!
Two figures are similar if
corresponding angles are
congruent and
corresponding sides are
proportional. The symbol
~ means is similar to.
∆ABC ~ ∆DEF
B
5
E
10
8
4
A 3 C
D
6
F
Corresponding
angles
Corresponding
sides
5 4 3
 
10 8 6
A  D
B  E
C  F
B
5
A
3
10
E
8
4
C
D
6
F
Example 1:
If ∆ABC ~ ∆DEF, find
the length of DF.
3 11 3n  49.5

4 .5 n
n  16.5
Example 2:
A rectangular picture window 12feet long and 6-feet wide needs
to be shortened to 9-feet in
length to fit a redesigned wall. If
the architect wants the new
window to be similar to the old
window, how wide will the new
window be?
12 6

9
n
n  4.5
12n  54
4.5 ft
Page 442
Guided Practice
#’s 3-5
Pages 440-441
with someone at
home and study
examples!
Homework: Page 442-443
#’s 6-15 all
#’s 18-27 all
Lesson Check 10-6
Page
588
Lesson 10-6
Study Guide and Review
Pages
462-464
#’s 6-22
(Odd answers in back of book)
Prepare for Test!
Pages
465
#’s 3-13, 16
```