题目内容
如图,AB切⊙O于点B,OA=
,∠A=30°,弦BC∥OA,则劣弧
的弧长为
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A.![]() | B.![]() | C.![]() | D.![]() |
A.
试题分析:连接OB,OC,
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∵AB为圆O的切线,
∴∠ABO=90°,
在Rt△ABO中,OA=

∴OB=
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∵BC∥OA,
∴∠OBC=∠AOB=60°,
又OB=OC,
∴△BOC为等边三角形,
∴∠BOC=60°,
则劣弧
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故选A.
考点: 1.切线的性质;2.含30度角的直角三角形;3.弧长的计算.
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