题目
(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:略