（2012?房山区二模）AB是圆O的直径，D为圆O上一点，过D作圆O的切线交AB延长线于点C，若DC=22，BC=2，则si
\uff082013?\u623f\u5c71\u533a\u4e8c\u6a21\uff09\u5982\u56fe\uff0cA\uff0cB\uff0cC\uff0cD\u662f\u2299O\u4e0a\u7684\u56db\u4e2a\u70b9\uff0c\u8fc7\u70b9B\u7684\u5207\u7ebf\u4e0eDC\u7684\u5ef6\u957f\u7ebf\u4ea4\u4e8e\u70b9E\uff0e\u82e5\u2220BCD=110\u00b0\u2235A\uff0cB\uff0cC\uff0cD\u662f\u2299O\u4e0a\u7684\u56db\u4e2a\u70b9\uff0c\u2234\u2220A+\u2220BCD=180\u00b0\uff0c\u2235\u2220BCD=110\u00b0\uff0c\u2234\u2220A=70\u00b0\uff0e\u2235BE\u4e0e\u2299O\u76f8\u5207\u4e8e\u70b9B\uff0c\u2234\u2220DBE=\u2220A=70\u00b0\uff0e\u6545\u9009B\uff0e
\uff081\uff09\u8bc1\u660e\uff1a\u8fde\u63a5AO\uff0cAC\uff08\u5982\u56fe\uff09\uff0e\u2235BC\u662f\u2299O\u7684\u76f4\u5f84\uff0c\u2234\u2220BAC=\u2220CAD=90\u00b0\uff0e\u2235E\u662fCD\u7684\u4e2d\u70b9\uff0c\u2234CE=DE=AE\uff0e\u2234\u2220ECA=\u2220EAC\uff0e\u2235OA=OC\uff0c\u2234\u2220OAC=\u2220OCA\uff0e\u2235CD\u662f\u2299O\u7684\u5207\u7ebf\uff0c\u2234CD\u22a5OC\uff0e\u2234\u2220ECA+\u2220OCA=90\u00b0\uff0e\u2234\u2220EAC+\u2220OAC=90\u00b0\uff0e\u2234OA\u22a5AP\uff0e\u2235A\u662f\u2299O\u4e0a\u4e00\u70b9\uff0c\u2234AP\u662f\u2299O\u7684\u5207\u7ebf\uff1b\uff082\uff09\u89e3\uff1a\u7531\uff081\uff09\u77e5OA\u22a5AP\uff0e\u5728Rt\u25b3OAP\u4e2d\uff0c\u2235\u2220OAP=90\u00b0\uff0cOC=CP=OA\uff0c\u5373OP=2OA\uff0c\u2234sinP=OAOP=12\uff0e\u2234\u2220P=30\u00b0\uff0e\u2234\u2220AOP=60\u00b0\uff0e\u2235OC=OA\uff0c\u2234\u2220ACO=60\u00b0\uff0e\u5728Rt\u25b3BAC\u4e2d\uff0c\u2235\u2220BAC=90\u00b0\uff0cAB=33\uff0c\u2220ACO=60\u00b0\uff0c\u2234AC=ABtan\u2220ACO=33tan60\u00b0=3\uff0e\u53c8\u2235\u5728Rt\u25b3ACD\u4e2d\uff0c\u2220CAD=90\u00b0\uff0c\u2220ACD=90\u00b0-\u2220ACO=30\u00b0\uff0c\u2234CD=ACcos\u2220ACD=3cos30\u00b0=23\uff0e
连接BD、OD，如下图所示：由已知中AB为圆O的直径，则∠ADB=90°
又∵CD为圆的切线，则CD2=CB?CA，即（2
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