(2006•泰安)(1)已知:如圖①,在△AOB和△COD中,OA=OB,OC=OD,∠AOB=∠COD=60°,求證:①AC=BD;②∠APB=60度;
(2)如圖②,在△AOB和△COD中,若OA=OB,OC=OD,∠AOB=∠COD=α,則AC與BD間的等量關(guān)系式為______;∠APB的大小為______;
(3)如圖③,在△AOB和△COD中,若OA=k•OB,OC=k•OD(k>1),∠AOB=∠COD=α,則AC與BD間的等量關(guān)系式為______;∠APB的大小為______.
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