⊙O2 diameter BF, connecting AF and AB.
Then < BAF = 90.
∴∠F+∠ABF=90
∫CE‖BD
∴∠ACE=∠D
∠∠ACE =∠ABE,∠D=∠F
∴∠ABE+∠ABF=90
∴∠EBF=90
∴BE is the tangent of O2.