如图,已知AD//BC,AD=BC,AE⊥AD,AF⊥AB,AE=AD,AB=AF.求证:AC=EF.

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如图,已知AD//BC,AD=BC,AE⊥AD,AF⊥AB,AE=AD,AB=AF.求证:AC=EF.
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如图,已知AD//BC,AD=BC,AE⊥AD,AF⊥AB,AE=AD,AB=AF.求证:AC=EF.
如图,已知AD//BC,AD=BC,AE⊥AD,AF⊥AB,AE=AD,AB=AF.求证:AC=EF.

如图,已知AD//BC,AD=BC,AE⊥AD,AF⊥AB,AE=AD,AB=AF.求证:AC=EF.
∵AD‖BC,AD=BC
∴ADCB为平行四边形
∴AD=BC=AE
∵AE⊥AD,AF⊥AB
∴∠BAF=∠DAE=90度
∴∠EAF+∠DAB=∠DAB+∠B
∴∠EAF=∠B
在△AEF与△BCA中
AE=BC
∠EAF=∠B
AF=BA
∴△AEF≌△BCA(SAS)
∴AC=EF

AE⊥AD,AF⊥AB 推出∠EAD=∠FAB=90
∠EAF=360-∠EAD-∠FAB-∠DAB
=180-∠DAB
AD//BC,AD=BC 推出 平行四边形ABCD 推出 ∠ABC=180-∠DAB
推出∠EAF=∠ABC
又AE=DE,AF=AB
等边三角行
AC=EF