As shown in the figure, in △ ABC, ab = AC, point E is on the extension line of Ca, and ED ⊥ BC is on D

As shown in the figure, in △ ABC, ab = AC, point E is on the extension line of Ca, and ED ⊥ BC is on D

It is proved that: ∵ AB = AC, ∵ B = ∵ C, ∵ ed ⊥ BC, ∵ BDF = ∵ CDF = 90 degree, ∵ B + ∵ BFD = 90 degree, ∵ C + ∵ e = 90 degree, ∵ BFD = ∵ e, ? BFD = ∵ AFE, ∵ e = ? AFE, AE = AF