Year 2 Warm-Up

1. A

B

CD

E

a. Is AEB~ADC? Why

b. Solve for x2

10

x

14

2. Are the two triangles similar? why?

15

18

10 12

Warm-Up Answers:

1. Yes, by AA (parallel lines imply congruent corresponding angles)x = 14/5 or 2.8

2. No, because the corresponding sides are not proportional.

11.3 Indirect Measurement/Applications

We can use similar triangles to calculate the height of tall objects that you can’t

reach. This is called indirect measurement.

Example #1

Example #1 ContinuedLets use what we know about similar triangles to

find the height of the lamp post.

1. Set up a proportion:

2. Simplify:

3. Cross multiply:

4. Solve:

6

18

525.

x

1

3

525.

x

x 1575.x = 15 feet 9 inches

1* 3*5.25x

Example #2

8 m

12 m

9 m

About how long is the log that goes across the creek?

Example #2 ContinuedLets use what we know about similar triangles to

find the length of the log

1. Set up a proportion:

2. Simplify:

3. Cross multiply:

4. Solve:

8 12

9x

8 4

3x

6x The log is 6 meters

4* 8*3x

Classwork Option 1:• Make a poster of the assigned problem

with all sides labeled

• Set up the proportion

• Solve

• Be prepared to present to the class

Problems:

pg 582 1,2,3,5,7, 10 pg 614 #7,

Classwork Option 2:Math Lab Group Activity…

Break up into groups of no more than 4 and make sure each member of your group has a

math lab handout.

You will need one meter stick for your group and something to write on and to write with.

Summary:If you were asked to find the height of this

flagpole…

What do you need to know to find the height?

And

What tools will you need?

Homework:

11.3 Worksheet