Similarity

16
Similarity

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Similarity. Triangles are similar if their corresponding angles are equal and their corresponding sides are proportional. TESTS FOR SIMILARITY. Two triangles are similar if: All corresponding angles are equal All the corresponding sides have the same ratio (proportional). - PowerPoint PPT Presentation

Transcript of Similarity

Page 1: Similarity

SimilaritySimilarity

Page 2: Similarity

TESTS FOR SIMILARITY

Two triangles are similar if:

• All corresponding angles are equal• All the corresponding sides have the same ratio

(proportional)

Triangles are similar if their corresponding angles are equal and their corresponding sides

are proportional

Page 3: Similarity

How To Identify?

Two triangles are similar if:

• 3 angles of 1 triangle are the same as 3 angles of the other

• 3 pairs of corresponding sides are in the same ratio

• 2 pairs of corresponding sides are in the same ratio and the included angle is equal

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Type 1: 3 angles of 1 triangle are the same as 3

angles of the other (AAA)

A

B C

D

E F

In triangle ABC, any 2 angles are equal to any 2 angles of triangle DEF, then they are similar.

g

h i

k

l

Angle g= angle k

Angle h= angle j

triangle ABC and DEF are similar

j

Angle i= angle l

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Type 2: 3 pairs of corresponding sides are in

the same ratio

A

B C

z

h

i

D

EF

In triangle ABC and DEF, if

kz

kh

ki

triangle ABC and DEF are similar.

where k is a constant.

kAC

DF

BC

EF

AB

DE

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Type 3: 2 pairs of corresponding sides are in the

same ratio and the included angle is equal (SAS) A

B

z

h

i

C

D

E

kz

kh

ki

F

triangle ABC and triangle DEF are similar.

g

h

In triangle ABC and DEF, if

kBC

EF

AB

DE

and angle g = angle h.

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1. Are the following triangles similar? Not drawn to scale.

A

B

C

D

E

F

75

40

40

65

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1. Are the following triangles similar? Not drawn to scale.

A

B

C

2

5

6

E

4

10

12

D

F

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B

1

4

3.5

A

B

E

2

5

7.5

F

D

1. Are the following triangles similar? Not drawn to scale.

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B

A

C

E

F

D

3.5

5

7

1055 55

1. Are the following triangles similar? Not drawn to scale.

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Think!

1 Which of the following triangles are always similar?

a.  right triangles

b.  isosceles triangles

c.  equilateral triangles

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Similar triangles are exactly the same shape and size.

A) True

B) False

2.

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The sides of a triangle are 5, 6 and 10.  Find the length of the longest side of a similar triangle whose shortest side is 15. A)10

B)15

C)18

D)30

3.

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4. In the diagram, DE is parallel to AC.  BD = 4, DA = 6 and EC = 8.  Find BC to the nearest tenth.

A) 4.3

B) 5.3

C) 8.3

D) 13.3

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5. Find BC.

A) 4

B) 4.5

C) 13.5

D) 17

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6. At a certain time of the day, the shadow of a 5' boy is 8' long.  The shadow of a tree at this same time is 28' long.  How tall is the tree?

A) 8.6

B) 16

C) 17.5

D) 20