∠BAD=∠CDF (Corresponding angles for parallel lines AB and CD)
∠BAD=∠CBE (Corresponding angles for parallel lines AB and CD)
Thus, ∠CDF=∠CBE (I)
We know, AD=BC (ABCD is a parallelogram)
and AD=DF (Given)
Thus, DF=BC (II)
Similarly, BE=CD (III)
Now, In △CDF and △CBE
∠CDF=∠CBE (From I)
FD=BC (From II)
BE=CD (From III)
Thus, △FDC≅△CBE (SAS rule)
△BEC≅△DCF