所示的梯形ABCD,AD∥BC,AD = 2,AB = 9,CD = 6,BC = 7,EF∥BC,和梯形EBCF AEFD梯形的周长等于EF所需的长度.

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所示的梯形ABCD,AD∥BC,AD = 2,AB = 9,CD = 6,BC = 7,EF∥BC,和梯形EBCF AEFD梯形的周长等于EF所需的长度.
所示的梯形ABCD,AD∥BC,AD = 2,AB = 9,CD = 6,BC = 7,EF∥BC,和梯形EBCF AEFD梯形的周长等于EF所需的长度.

所示的梯形ABCD,AD∥BC,AD = 2,AB = 9,CD = 6,BC = 7,EF∥BC,和梯形EBCF AEFD梯形的周长等于EF所需的长度.
让AE
= X,DF = Y,那么EB = 9-X,FC = 6-Y,∵AD∥EF∥BC,∴AE:EB = DF:FC,即:①X:(9-X)= Y
:(6-y)的,得到的两个梯形的周长相等:②2 + x + y的= 9-7 +6- y,则①,②得到的溶液:X = 6时,y =
4,通过D点AB,平行线,交叉EF,BC在M,N点,那么AD = EM = BN = 2,△DMF∽△DNC,∴分子式:NC = DF:DC,解决:MF
= 10/3,∴ EF = 2 10/3 = 16/3