已知：如图,EF‖BC,AE²=AD·AB.求证：DF‖EC.【EF‖BC,平行线分直线,成比例AE/AB=AF/AC,AE²=AD·AB,AD/AE=AE/AB=AF/ACDF‖EC】这是解法、可是为什么AD/AE=AE/AB=AF/AC,DF就平行EC、要理由

已知：如图,EF‖BC,AE²=AD·AB.求证：DF‖EC.【EF‖BC,平行线分直线,成比例AE/AB=AF/AC,AE²=AD·AB,AD/AE=AE/AB=AF/ACDF‖EC】这是解法、可是为什么AD/AE=AE/AB=AF/AC,DF就平行EC、要理由
已知：如图,EF‖BC,AE²=AD·AB.求证：DF‖EC.
【
EF‖BC,平行线分直线,成比例
AE/AB=AF/AC,
AE²=AD·AB,AD/AE=AE/AB=AF/AC
DF‖EC
】这是解法、可是为什么AD/AE=AE/AB=AF/AC,DF就平行EC、要理由

已知：如图,EF‖BC,AE²=AD·AB.求证：DF‖EC.【EF‖BC,平行线分直线,成比例AE/AB=AF/AC,AE²=AD·AB,AD/AE=AE/AB=AF/ACDF‖EC】这是解法、可是为什么AD/AE=AE/AB=AF/AC,DF就平行EC、要理由
AD/AE=AE/AB=AF/AC可知AD/AE=AF/AC,三角形ADF相似于三角形AEC,DF就平行EC