Question

Cho hình thang ABCD(AB//CD) có AB = 7cm, CD=12cm. Gọi M là trung điểm của CD, E là gia điểm của MA và BD, F là giao điiểm của MB và AC.

 a, chứng minh EF // với AB 

b, tính độ dài đoạn EF

 

Answer 1

BFFM=ABCM(1)" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">AEEM=ABDM(2)" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">ABDM=ABMC(3)" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">AEEM=BFFM" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">AEEM=BFFM" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">MEAM=DMAB" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">EFAB=MEAM" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">DMAB=ÈFAB⇒EF=DM=122=6cm" role="presentation" tabindex="0" style="border:0px; box-sizing:border-box; direction:ltr; display:inline; float:none; font-size:16px; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:0px; position:relative; text-align:left; white-space:nowrap; word-spacing:normal">DM/AB=EF/AB⇒EF=DM=12/2=6cm