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Presentation Transcript

,

D

A

E

F

B

C

A

B

F

E

C

D

A

A

B

F

E

C

E

F

B

C

∵太阳的光线是平行的

∴ AB∥DE

∴∠ABC= ∠DEF

∵人与旗杆是垂直于地面的

∴∠ACB= ∠DFE=900

∴△ABC∽△DEF

E

1

3

2

A

M

N

B

F

D

H

E

A

2

M

N

3

B

F

D

H

∵人、标杆和旗杆是互相平行的

∵EF∥CN

∴ ∠1= ∠2

∴△AME∽△ANC

1

∵人与标杆的距离AM、人与旗杆的距离AN、标杆与人眼到地面距离的差EM都可测量出

∴能求出CN

∵四边形ABND为矩形

∴DN=AB

∴能求出旗杆CD的高度CD=CN+DN

C

A

A

1

2

B

E

D

B

E

D

A

∴∠ABC=∠A'B' C'

∴ ∠ACB =∠ C'=90º

∴△ABC∽△ A'B' C'

∴AC=6

AE=AC+CE=6+2=8

A'

C'

B'

C

B

E

D

A

A'

1

?

B

C'

E

B'

1.5

2

C

D

9

A

A'

?

B

C

1

2

C'

E

9

B'

D

1.5

∴四边形ACDB为平行四边形

∴旗杆的上半部分AC与墙上的影子BD的长度是相同的

A

C

A'

B

1

2

C'

E

B'

1.5

9

D

A

A'

B

1

2

C'

E

1.5

9

B'

A

A'

B

1

2

C'

60

E

1.5

9

B'

Q

B

A

C

O

P

1 、 测高(不能直接使用皮尺或刻度尺量的)

2 、 测距(不能直接测量的两点间的距离)

③利用相似解决问题

PN

=

BC

80–x

x

=

80

120

A

E

N

P

C

B

Q

D

M