(本题满分8分)如图,AB是⊙O的直径,过B点作⊙O的切线,交弦AE的延长线于点C,作,垂足为D,若,,求DE的长.

(本题满分8分)如图,AB是⊙O的直径,过B点作⊙O的切线,交弦AE的延长线于点C,作,垂足为D,若,,求DE的长.

题型:不详难度:来源:
(本题满分8分)如图,AB是⊙O的直径,过B点作⊙O的切线,交弦AE的延
长线于点C,作,垂足为D,若,求DE的长.
答案
解法一:∵BC是⊙O的切线,     ∴
在Rt△ABC中,∵,∴
.··············································································· 3分
在Rt△AOD中,,∴.···· 6分
,   ∴.··························································· 8分
解法二:连接BE.∵AB为直径,∴
.∴.·········································· 3分
在Rt△ABC中,∵
. ∴.························································ 6分
,         ∴.·················································· 8分
解析

举一反三
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径作圆,交AC于另一点E,交AB于点FG,连接EF.若
BAC=22°,则∠EFG_  ▲  
题型:不详难度:| 查看答案
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题型:不详难度:| 查看答案
(本题满分10分)如图,在△ABC中,∠C= 90°,以AB上一点O为圆心,
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题型:不详难度:| 查看答案
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题型:不详难度:| 查看答案
如图,的弦与直线径相交,若,则=_____°.
题型:不详难度:| 查看答案
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