⊙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.