In the given figure, side BC of ΔABC is bisected at D and O is any point on AD, BO and CO produced meet AC and AB at E and F respectively, and AD is produced to X so that D is the midpoint of OX. Prove that AO : AX = AF : AB and show that EF || BC.
Given BD = CD and OD = DX
Join BX and CX
Thus, the diagonals of quad OBXC bisect each other
OBXC is a parallelogram
BX || CF and so, OF || BX
Similarly, CX || OE
In ΔABX, OF || BX
Therefore,
AO/AX=AF/AB—– (1)
In ΔACX, OE || XC
Therefore,
AO/AX=AE/AC—– (2)
From (1) & (2) we get:
AF/AB=AE/AC
Hence, EF || BC