如图,已知点E是正方形ABCD边AD的中点,现将△ABE沿BE所在直线翻折成到△A'BE,使A’C=BC,并连接A'C,A'D.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/9/9e6dfc22-d7d9-425a-9960-4282852e0927.png?resizew=283)
(1)求证:DE∥平面A'BC;
(2)求证:A'E⊥平面A'BC.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/9/9e6dfc22-d7d9-425a-9960-4282852e0927.png?resizew=283)
(1)求证:DE∥平面A'BC;
(2)求证:A'E⊥平面A'BC.
更新时间:2019-04-17 20:21:43
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解答题-证明题
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【推荐1】如图,四棱锥
中,
,底面
是梯形,AB∥CD,
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.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/1/a5639e89-81bc-4ab1-ab15-3d4a00b6bf12.png?resizew=156)
(1)若
MN∥平面PAD;
(2)若直线AN与平面PBC所成角的正弦值为
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(1)若
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(2)若直线AN与平面PBC所成角的正弦值为
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【推荐2】如图,平行四边形
中,
=
=
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沿
折起,得到三棱锥
,且
,点
为侧棱
的中点.
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(1)求证:
平面
;
(2)求三棱锥
的体积;
(3)在
的角平分线上是否存在一点
,使得
平面
?若存在,求
的长;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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【推荐1】如图,在直四棱柱ABCD–A1B1C1D1中,已知底面ABCD是菱形,点P是侧棱C1C的中点.
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(1)求证:AC1∥平面PBD;
(2)求证:BD⊥A1P.
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(1)求证:AC1∥平面PBD;
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解答题-问答题
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【推荐2】如图,在四棱锥
中,
平面
,
,
,
,
,
,
是
的中点.
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(1)证明:
平面
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解题方法
【推荐3】如图,在四棱锥
中,底面
为正方形,
底面
,
,
为线段
的中点,
为线段
上的动点.
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(1)若平面
交
于点
,求证:
;
(2)求证:
平面
;
(3)判断直线
与平面
所成角的大小是否可以为
,并说明理由.
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(1)若平面
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