Question

已知:如图,在梯形ABCD中,AD‖BC,AC与BD相交于点O,过O作MN‖BC,分别交AB,DC与点M,N

Answer 1

1、∵MN∥BC

∴∠AMO=∠ABC,∠AOM=∠ACB；∠DON=∠DBC,∠DNO=∠DCB

∴△AOM∽△ACB；△DON∽△DBC

∴OM/BC=AO/AC,ON/BC=OD/BD

∵AD∥BC

∴∠DAO=∠OCB,∠ADO=∠OBC

∴△AOD∽△BOC

∴OD/OB=OA/OC

即OD/BD=OA/AC

∴OM/BC=ON/BC

∴OM=ON

第二题还没看= = 骚等