The line segment joining the mid - points of any two sides of a triangle is parallel to the third side and equal to half of it.
In the given figure, the side AC of ΔABC is produced of E such that CE=12AC. If D is the mid - points of BC and ED produced meets AB at F and CP, DQ are drawn parallel to BA, then FD =
13FE
In ΔABC, D is the mid - point of BC and DQ∥BA.
∴ Q is the mid - point of AC.
[Converse of mid-point theorem]
⇒AQ=QC
Now, FA∥DQ∥PC, and AQC is the transversal such that AQ =QC and FDP is the other transversal on them.
∴ FD =DP ….(1) [By intercept theorem]
Now, EC=12AC=QC
∴ In EQD, C is the mid-point of EQ and CP∥DQ
∴ P must be the mid-point of DE.
∴ DP = PE
Thus, FD = DP = PE [From (1) and (2)]
Hence, FD=13FE