若是非零向量且满足（ ）⊥，，则与的夹角是 （     ）

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='20429' and id < 1878687 and id<>'1878687' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='20429' and id > 1878687 and id<>'1878687' order by id asc limit 5