a=1∠120°为旋转因子，1+a+a^2 等于多少(  )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69497' and id < 4501903 and id<>'4501903' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69497' and id > 4501903 and id<>'4501903' order by id asc limit 5