如图在梯形ABCD中AD平行BC,AC,BD相交于点O,过O点作BC的平行线分别交AB,CD于点E,F
问题补充说明:(1)求证:OE=OF(2)若AD=3,BC=4,求EF的长。
(1上色配如会益训西)易证△AOD~△COB△BOE~△BDA△COF~△CAD
∴CO/AO=BO/DO合比性质可得CO/AC=BO/BD
∵OB/BD=OE/ADOC/AC=OFAD
∴OE/AD=OF/AD
∴OE=只意八算践态松难案行硫OF
(2)由(1)可得OB/OD=BC/AD=4/3
∴OE/AD=OB/BD=4/7
OE/3=4/7OE=1准众地管输石赵只提两2/7
∴EF=2OE=24/7
标签:BC,于点,ABCD