如图,在长方体
中,
,AB=2,点E是线段AB的中点.
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/7ca12627e72a42c997eeab59b200bb0a.png)
(1)求证:
;
(2)求二面角
的大小的余弦值.
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/e656584afafc4d7e96d8037895fe13cb.png)
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/924c3854afe1497e89590e9de9fdd5d9.png)
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/7ca12627e72a42c997eeab59b200bb0a.png)
(1)求证:
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/327512039a3d423491de35753bf8b85c.png)
(2)求二面角
![](https://img.xkw.com/dksih/QBM/2016/2/23/1572493694836736/1572493700628480/STEM/d173dc7994e5424f97dc8b52de60345f.png)
更新时间:2016-12-04 02:29:32
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【推荐2】如图,在正方体
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名校
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