### File

```Warm-up
• Make sure to grab a red pen and be ready to
Today
Squawk like a CHICKEN!
Discussion
Practice problems
7.6: Indirect Measurement and
Obj: _______________________
___________________________
Indirect Measurement
• Measuring the distance of something without
physically measuring it
Using Similar Triangles to Measure
Distance
8.5 Indirect Measurement and Additional Similarity Theorems
Key Skills
Use similar triangles to measure distance
indirectly.
Estimate the width of the lake.
Finding Distance Indirectly
ROCK CLIMBING
are at an
indoor
climbing
wall.
To estimate
of
SimilarYou
triangles
can
be used
to find
distances
thatthe
areheight
difficult
the wall, youto
place
a mirror
on the floor 85 feet from the base of the wall. Then
measure
directly.
you walk backward until you can see the top of the wall centered in the mirror.
You are 6.5 feet from the mirror and your eyes are 5 feet above the ground.
D
B
5 ft
Not drawn to scale
A
6.5 ft
C
85 ft
E
Finding Distance Indirectly
Use similar triangles to estimate
the height of the wall.
SOLUTION
DE EC
Ratios of lengths of
=
corresponding sides are equal.
BA AC
So,
the height of the wall is about 65 feet.
DE = 85
Substitute.
5
6.5
D
Multiply each side by
5 and simplify.
65.38  DE
B
5 ft
A
6.5 ft
C
85 ft
E
• Kim wants to know the height of a basketball
hoop. The regulation height is 10 ft. Use
Kim’s height and length of the shadows to
find the height of the basketball hoop. Is the
hoop at regulation height?
• She is 70” and casts a 50” shadow, the
• At a certain time of day, a 6ft man casts a 4 ft
shadow. At the same time of day, how tall is
a tree that casts an 18 ft shadow?