Question在 $\square A B C D$ 中, $A C, B D$ 交于点 $O$, 点 $E, F$ 在 $A C$ 上, $A E=C F$。证明四边形 $E B F D$ 是平行四边形和菱形。

Studdy Solution
Since $ED = FD$ and we have already proven that $EB = FB$, we can say that $EBFD$ is a rhombus because all sides are equal.
The quadrilateral $EBFD$ is a parallelogram and if $\angle BAC = \angle DAC$, then $EBFD$ is a rhombus.