如图(1)所示,在边长为12的正方形
中,点B、C在线段AA′上,且AB=3,BC=4.作BB1
AA1,分别交A1A1′、AA1′于点B1、P;作CC1
AA1,分别交A1A1′、AA1′于点C1、Q.现将该正方形沿BB1,CC1折叠,使得
与AA1重合,构成如图(2)所示的三棱柱ABC-A1B1C1.
![](https://img.xkw.com/dksih/QBM/2015/1/5/1571945279684608/1571945285361664/STEM/6d7200a0e7f94302a60aba717033a51b.png?resizew=226)
(1)在三棱柱ABC-A1B1C1中,求证:AP⊥BC;
(2)在三棱柱ABC-A1B1C1中,连接AQ与A1P,求四面体AA1QP的体积;
(3)在三棱柱ABC- A1B1C1中,求直线PQ与直线AC所成角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b00a29c3e8e4038d79cbe03d5f5bddd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895d6f710d5f67e1d4c7408d50d77281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895d6f710d5f67e1d4c7408d50d77281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/986a4ffb456a7da8be680400f80de85c.png)
![](https://img.xkw.com/dksih/QBM/2015/1/5/1571945279684608/1571945285361664/STEM/6d7200a0e7f94302a60aba717033a51b.png?resizew=226)
(1)在三棱柱ABC-A1B1C1中,求证:AP⊥BC;
(2)在三棱柱ABC-A1B1C1中,连接AQ与A1P,求四面体AA1QP的体积;
(3)在三棱柱ABC- A1B1C1中,求直线PQ与直线AC所成角的余弦值.
更新时间:2016-12-03 07:53:46
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解答题-证明题
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【推荐1】如图,在直三棱柱
中,
是棱BC上一点(点D与点
不重合),且
,过
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;
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(2)若
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【推荐2】如图,在正四面体ABCD中,E是棱AD的中点,P是棱AC上一动点,
的最小值为
.
(2)当
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【推荐1】如图1,由正方形
与正三角形
组成的平面图形,其中
,将其沿
,
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,
恰好重合于点
,如图2.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/25/1b8d5b28-40bb-4d6d-8c3f-3346d05fe7fc.png?resizew=280)
(1)证明:平面
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【推荐2】如图,在四棱锥
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【推荐3】如图,在四棱锥
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【推荐1】如图,直三棱柱的底面是等腰直角三角形,
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【推荐2】已知直角梯形
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![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/3/632e7964-ed70-4f80-99d0-7c868d74381c.png?resizew=285)
(1)求异面直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cdba1337ec85fa9722cb4b320a82ae6.png)
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(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/27298fab52d282c92ca30fd0a9878c80.png)
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【推荐3】在三棱锥
中,
平面
,平面
平面
.
(1)证明:
平面
;
(2)若
为
中点,求向量
与
夹角的余弦值.
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
(2)若
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