In given figure
ABCD is a parallelogram and
ABEF is a rectangle .
Then AF=BE (opposite side of rectangle ).....................(1)
And AD=BC (opposite side of parallelogram )...................(2)
∠AFE=∠AFD=∠BEF=∠BEC=900 (angle of rectangle ABEF)....................................(3)
ΔAFD and ΔBEC
∠AFD=∠BEC=900..(From 3)
AF=BE (From 1)
AD=BC (From 2)
∴ΔAFD≅ΔBEC