In δδABE and δδCBF,

AB=BC，

∠ Abe =∠CBF=90,

AE=CF，

∴rtδabe≌rtδcbf(hl)，

⑵∫AB = BC∠ABC = 90，

∴∠BAC=∠BCA=45，

∫∠CAE = 30，

∴BCE= 15，

Congruence from (1): ∠ BCF = ∠ BAE = 15,

∴∠ACF=75 .