It is known that, as shown in the figure, the quadrilateral ABCD is a diamond, f is a point on AB, DF intersects AC with E

It is known that, as shown in the figure, the quadrilateral ABCD is a diamond, f is a point on AB, DF intersects AC with E

It is proved that: the ∵ quadrilateral ABCD is a diamond, BC = CD, ab ∥ CD, and ∥ AFD = CDE. In △ BCE and △ DCE, BC = CD, BCE = dcece = CE ≌ BCE ≌ DCE, CBE = CDE, AFD = CDE, AFD = CBE