下图所示某非正弦周期电流，其频率为（）。 

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SQL Error: select id,body,options from ***_enewstiku where sourceid='32635' and id < 2595022 and id<>'2595022' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='32635' and id > 2595022 and id<>'2595022' order by id asc limit 5