在如图所示的多面体中,
平面
,四边形
为平行四边形,点
分别为
的中点,且
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/25/a7662aef-6df9-4089-b456-031049af6258.png?resizew=190)
(1)求证:
平面
;
(2)若
,求该多面体的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca5dd496ee0c1170ef6dcc48266ee444.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/218054144a13435580cd132b9459546c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad056c25c0fdcbcc765eb5cbc6093f2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54032c35995fca06253098de5e4f8ff8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0d5a2cd05e4476fc72271e8fdb59a9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4775eb97d296048272d85829ea6474b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c31e6af4a2b5870366b9774e938bfe1.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/25/a7662aef-6df9-4089-b456-031049af6258.png?resizew=190)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57f9d682e5d3cc8573574d8d11636758.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/218054144a13435580cd132b9459546c.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c91153987852dcb546b415c78999f939.png)
更新时间:2020-06-03 19:34:27
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【推荐1】已知某个几何体的三视图如图所示,根据图中的尺寸,
求:(1)这个几何体的体积是多少?
(2)这个几何体的表面积是多少?
求:(1)这个几何体的体积是多少?
(2)这个几何体的表面积是多少?
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解答题-证明题
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【推荐2】如图,
是边长为4的正三角形,D,E分别是边AB,AC的中点,以DE为折痕把
折起,使点A到达点P的位置,且
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![](https://img.xkw.com/dksih/QBM/2021/1/7/2630910734589952/2633062221832192/STEM/a5fd834f-391c-48db-a994-d7b6ff9be81a.png?resizew=237)
(1)求证:
平面PEC
(2)求三棱锥
的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f22f74a1995a5b5fa2a0536606ce1df.png)
![](https://img.xkw.com/dksih/QBM/2021/1/7/2630910734589952/2633062221832192/STEM/a5fd834f-391c-48db-a994-d7b6ff9be81a.png?resizew=237)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c14a7920527b3b5cc019910af3a3cf5.png)
(2)求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31ed9b5930aff911cbecc862a72d7173.png)
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解答题-证明题
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解题方法
【推荐1】如图,在三棱锥
中,
分别是
,
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/23/971340bc-55e2-40fc-89a9-04c963972000.png?resizew=161)
(1)求证:
平面
;
(2)在图中作出点
在底而
的正投影,并说明作法和理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d212e6c0b08ce1ce1adce727a902d17b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/23/971340bc-55e2-40fc-89a9-04c963972000.png?resizew=161)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/063510e3c1fb6a7ccc3b8e3e3c7d660e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
(2)在图中作出点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
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解题方法
【推荐2】正三棱柱
的底面正三角形的边长为1,D为线段
上的动点,
.
(1)当D为
中点时,证明:
//平面
;
(2)当D在线段
上移动时,求
周长的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6db57eca2a7cbd91bc57372592580a76.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/14/7354bf80-7ebc-425f-94cf-ed73dc48eabf.png?resizew=195)
(1)当D为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e26d9636ad77369535852c6e4493446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ba9e20d667d04bf3ee7f55cc795ce01.png)
(2)当D在线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fdd324f113250febd154c16648ac6533.png)
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【推荐3】在矩形
中,
,点P是线段
的中点,将
沿
折起到
位置(如图),使得平面
平面
,点Q是线段
的中点.
(1)证明:
平面
;
(2)求平面
与平面
所成角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5181b97a7e43959b8455680157c3b644.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/357265c532428e886a643e8e653eec9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63a253c7fdf589ee3dece13d5b5b5732.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dda72c058454c71f55aba95844a501dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/561434718c09d44394f583928f27a429.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2bdc60a42a1addaf772c18972e576fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be2e2c0d4ac2bd79f6cea7a9b1a50662.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/5/161a222f-f43d-4953-8209-1cac57f9ca3e.png?resizew=157)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0a66d1d242f5317fcc90fee9a8e9fa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f200cca4c2a438b59c592a7edb214e8.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f35614aff055b98b76ca262f64e629d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2246c0e92e8cc344f636ea8f8f9037e6.png)
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