解答题-证明题 适中0.64 引用1 组卷793
如图,在直三棱柱
中,
平面
,其垂足
落在直线
上.
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/91514cf03eb34841ba27de20b50e27ab.png)
(Ⅰ)求证:
⊥
;
(Ⅱ)若
,
,
为
的中点,求二面角
的平面角的余弦值.
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/703d34dc70f14ab0905085520129effa.png)
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/91514cf03eb34841ba27de20b50e27ab.png)
(Ⅰ)求证:
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/683c67f95a7b433f881c2aad9b83a800.png)
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/b5c1d09352ef44849bce661f7e7e0e55.png)
(Ⅱ)若
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/c5bf0b8e79d04191bafdea9fca71a0a5.png)
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/962daaad6043420aac105deec2e3b36e.png)
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/ffd71427b1f04839a75660f7b33524b2.png)
![](https://img.xkw.com/dksih/QBM/2015/11/19/1572300353937408/1572300359811072/STEM/7326d6cb19bb489d99e17258c390063b.png)
15-16高三上·浙江温州·阶段练习
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