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Who can work out some math problems in junior high school? Please ask for as much as possible.
As shown in the figure, straight line AB passes through point C on ⊙O, OA=OB, CA=CB, and ⊙O intersects straight line OB at E and D, connecting EC and CD.

(1) Verification: straight line AB is tangent to ⊙O;

(2) Try to guess the equivalence relation among BC, BD and BE, and prove it;

(3) If tan∠CED=? The radius ⊙O is 3. Find the length of OA.