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 .