∵ Quadrilateral ABCD is a parallelogram

∴ AB // CD

∴∠eao =∞∠fco (two straight lines are parallel and the internal dislocation angles are equal)

And ∵ AC is the diagonal of the parallelogram ABCD.

∴ O = Company

∠AOE = ∠COF (equal to vertex angle)

∴ △AOE = △COF (corner kick ASA)

∴ AE = CF

(2) If it is still in the parallelogram ABCD, the conclusion is the same.

In fact, as long as it is AB // CD and point O is the midpoint of AC, the conclusion is still the same, AE = CF