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# 二面角 - PowerPoint PPT Presentation

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## 二面角

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Presentation Transcript

?

O

A

B

B

B

B

B

B

B

l

l

α

α

1 、半平面——

α

ι

β

2、二面角的定义

B

A

l

O1

O

∠A O B

∠A1O1B1

B1

B

A1

A

9

α

ι

β

00-两个半平面重合

1800 –两个半平面同一水平面

P

C

A

B

1、如图，AB是圆的直径，PA垂直圆所在的平面，C是圆上任一点，则二面角P-BC-A的平面角为:

A.∠ABP B.∠ACP C.都不是

D1

C1

B1

A1

C

D

B

A

ABCD－A1B1C1D1中，

ABCD所成的角

（2）二面角A－B1D1－C的大

P

O

P

C

A

B

A、B、C、D、

2

2

D

o

α

ι

α

ι

β

β

p

ι

β

α

P

B

A

A

B

“一作二证三求”