(2009•宁波)已知:如图,⊙O的直径AB与弦CD相交于E,
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=
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,⊙O的切线BF与弦AD的延长线相交于点F.
(1)求证:CD∥BF.
(2)连接BC,若⊙O的半径为4,cos∠BCD=
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,求线段AD、CD的长.
考点分析:
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