1 . 工人师傅要用铁皮做一个上大下小的正四棱台形容器(上面开口),使其容积为208立方分米,高为4分米,上口边长与下底面边长的比为5∶2,做这样的容器需要多少平方米的铁皮?(不计容器的厚度和加工余量,不要求写出已知、求解,直接求解并画图即可)
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2 . 如图,在棱长均为
的三棱柱
中,点
在平面
内的射影
为
与
的交点,
、
分别为
,
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/4dcf618a-1664-4df2-88f8-f81efd99422b.png?resizew=249)
(1)求证:四边形
为正方形;
(2)求直线
与平面
所成角的正弦值;
(3)在线段
上是否存在一点
,使得直线
与平面
没有公共点?若存在求出
的值.(该问写出结论即可)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9b7b7793d29d66dfdd89e7a6564a35c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b470c4e195cf7a07b7a331ce4b436e03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e26d9636ad77369535852c6e4493446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f1f229274a6e17977cc047814212589.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/4dcf618a-1664-4df2-88f8-f81efd99422b.png?resizew=249)
(1)求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9b7b7793d29d66dfdd89e7a6564a35c.png)
(2)求直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e53b212640dadf751ef7f65a78a209.png)
(3)在线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b470c4e195cf7a07b7a331ce4b436e03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74bca84ad86c648d3bb20c8909c8da3f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e21468a972babcefc0028f2bd1f56336.png)
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3 . 正多面体也称柏拉图立体,被誉为最有规律的立体结构,其所有面都只由一种正多边形构成的多面体(各面都是全等的正多边形,且每一个顶点所接的面数都一样,各相邻面所成二面角都相等).数学家已经证明世界上只存在五种柏拉图立体,即正四面体、正六面体、正八面体、正十二面体、正二十面体.已知一个正四面体
和一个正八面体
的棱长都是
(如图),把它们拼接起来,使它们一个表面重合,得到一个新多面体.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/31/661893bd-5cfb-4add-97f2-8b6d8e878a6d.png?resizew=283)
(1)求新多面体的体积;
(2)求正八面体
中二面角
的余弦值;
(3)判断新多面体为几面体?(只需给出答案,无需证明)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cb6c9306a25f041d7801274838b43dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c87bc797aad25e4ccdc9d722a87b642c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/31/661893bd-5cfb-4add-97f2-8b6d8e878a6d.png?resizew=283)
(1)求新多面体的体积;
(2)求正八面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00947c195caa8a846693b1d79a8835c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4b820c84570da9c38d0a81c22788b76.png)
(3)判断新多面体为几面体?(只需给出答案,无需证明)
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