10-11高三·安徽合肥·阶段练习
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1 . 如图,长方体ABCD﹣A1B1C1D1中,DA=DC=2,
,E是C1D1的中点,F是CE的中点.
(1)求证:EA∥平面BDF;
(2)求证:平面BDF⊥平面BCE;
(3)求二面角D﹣EB﹣C的正切值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cd35124a6f8e8fe6c6af0a5700b3ab4.png)
(1)求证:EA∥平面BDF;
(2)求证:平面BDF⊥平面BCE;
(3)求二面角D﹣EB﹣C的正切值.
![](https://img.xkw.com/dksih/QBM/2011/3/23/1570056926019584/1570056931016704/STEM/7b1d1574741b4276af895ad43f61261b.png?resizew=134)
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