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# 八年级数学 - PowerPoint PPT Presentation

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## 八年级数学

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### 八年级数学

(1)平行四边形有哪些性质?矩形与平行四边形比较有哪些特殊的性质?

A

B

D

C

S菱形ABCD= AC×BD

### 菱形的 识别

+

+

O

∵四边形ABCD是平行四边形

∴AO = OC

(已知)

∴ AB = BC

(垂直平分线的性质)

(菱形的定义)

∴平行四边形ABCD是菱形

+

A

B

D

C

A

B

D

C

A

B

C

D

AC⊥BD

A

F

E

B

D

C

3

1

2

DE∥AC交AB于E，DF∥AB交AC于F，

DE∥AC

DF∥AB

∠2=∠3

DE∥AC

∠1 =∠3

∠1 =∠2

AE=DE

AEDF是菱形

A

B

O

D

C

D

C

O

A

B

1、一个角是直角

2、对角线相等

1、一组邻边相等

2、对角线互相垂直

1、一个角是直角

2、对角线相等

1、正确使用判定定理；

2、完整书写证明格式。