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As shown in the figure, in △ ABC, ad ⊥ BC, be ⊥ AC, the perpendicular feet are D and e respectively. AD and be intersect at point F. if BF = AC, find the size of ∠ ABC
⊥ ad ⊥ BC, be ⊥ AC (known), ⊥ ADB = ⊥ ADC = ⊥ BEC = 90 ° (vertical definition), and ⊥ AFE = ⊥ BFD (equal to vertex angle), ⊥ AEF ⊥ BDF (similar to two triangles with equal corresponding angles), ⊥ FAE = ⊥ FBD (equal to corresponding angles of similar triangles). In △ BFD and △ ACD, ⊥ BDA = ⊥ ADC (proved) ⊥ FBD = ⊥ FAE (proved) BF = AC (known), ⊥ B FD ≌ △ ACD (AAS), ｜ BD = ad (the corresponding sides of congruent triangles are equal), ｜ bad = ∠ abd (equal sides and equal angles), and
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