Solving Similar Triangles

Learning Goals

By the end of the class I will be able to:

• ​

Warm up

Which triangles are similar? How do you know?

a

b

c

d

30^o

40^o

60^o

50^o

It’s Not all about the angles

The angles are not all that make the triangles similar. The sides are also proportional:

ΔABC ~ ΔDEF

​

A

B

C

D

E

F

It’s Not all about the angles

ΔABC ~ ΔDEF

​

How Do we Use it?

1.

2.

3.

12.5 cm

8 cm

16 cm

6.5 cm

How Do we Use it?

4.

5.

6.

Let’s Practice

1. Label your triangles

2. Set up your ratios

3. Substitute any information you have

4. Choose 1 of pair of ratios

5. Cross multiply

6. Finish solving (divide)

4

9

12

10

Try it Yourself. Find all missing sides

1. Label your triangles

2. Set up your ratios

3. Substitute any information you have

4. Choose 1 of pair of ratios

5. Cross multiply

6. Finish solving (divide)

3

8

16

11

Try it Yourself. Find all missing sides

1. Label your triangles

2. Set up your ratios

3. Substitute any information you have

4. Choose 1 of pair of ratios

5. Cross multiply

6. Finish solving (divide)

5

5.5

15

21

Try it Yourself. Find all missing sides

1. Label your triangles

2. Set up your ratios

3. Substitute any information you have

4. Choose 1 of pair of ratios

5. Cross multiply

6. Finish solving (divide)

22

17

35

40