9.1 Properties of Similar FiguresLearning Objective: To use ratios and proportions to find measures of similar

figures and use scale models to find dimensions of objects.

Notes

Learning Objective: To use ratios and proportions to find measures of similar figures and use scale models to find dimensions of objects.

EX 1 – Tell whether the shapes are similar. Explain!

Similar figures•Corresponding angles are congruent

•Corresponding sides are in proportion

a.

S

T

U

10

X

V

W15

15

59º

No!

Corresponding angles are not congruent

is equilateral, STU

all angles are 60º.

Learning Objective: To use ratios and proportions to find measures of similar figures and use scale models to find dimensions of objects.

b. L

C

R

M N

B3.2

D

3.2

2.52.5

2.5

4.5

9

5

,L M C R all rt. s N N

reflexive propNBR NDC all quads = 360

90 90 360m N m B

90 90 360m N m D 90 90 90 90m N m B m N m D

transitive prop

m B m D subtraction prop

all s are Are the sides in proportion?

Learning Objective: To use ratios and proportions to find measures of similar figures and use scale models to find dimensions of objects.

L

C

R

M N

B3.2

D

3.2

2.52.5

2.5

4.5

9

5

LC

MR

5

2.5 2

CD

RB

9

4.5 2

DN

BN

6.4

3.2 2

LN

MN

5

2.5 2

Yes! LNDC MNBR

Learning Objective: To use ratios and proportions to find measures of similar figures and use scale models to find dimensions of objects.

EX 2 – A school band designed a new insignia for the back of their uniforms. A scale drawing of the insignia was made with a scale of 4:7. The insignia in the scale drawing is 5 cm wide and 12 cm tall. The insignia will be 8.75 cm wide on the uniforms. Find the height of the insignia.

height

width12

5

8.75

h

5h105h 21

4

7 12

21

check

HW – p. 449

#1-18, 26-28

Out – Compare and contrast similar and congruent figures.

Summary – Something new I learned was…

POW!!