题目内容
(满分12分)如图,已知是⊙O的直径,是弦,过点作OD⊥AC于,连结.
小题1:(1)求证:;
小题2:(2)若,求∠的度数.
小题1:(1)求证:;
小题2:(2)若,求∠的度数.
小题1:证法一:是⊙O的直径
······················· (2分)
又
······················· (4分)
······················ (6分)
证法二:是⊙O的直径
················ (2分)
即
又 ······················ (3分)
··················· (4分)
···················· (5分)
小题2:(2)(6分)
解:是⊙O的直径,
······················· (3分)
略
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