Let $ABCD$ be a convex quadrilateral $\measuredangle ADC = \measuredangle BCD > 90$. Let $E$ be the point in which line $AC$ intersects the line parallel to $AD $ through $B$ and Let $F$ be the point in which line $BD$ intersects line parallel to $BC$ through $A$. Prove $EF||CD$.
I have tried multiple ways to prove this but am not arriving at the proof. Kindly give some hint or help me in solving this question