名校
解题方法
1 . 材料1.类比是获取数学知识的重要思想之一,很多优美的数学结论就是利用类比思想获得的.例如:若
,
,则
,当且仅当
时,取等号,我们称为二元均值不等式.类比二元均值不等式得到三元均值不等式:
,
,
,则
,当且仅当
时,取等号.我们经常用它们求相关代数式或几何问题的最值,某同学做下面几何问题就是用三元均值不等式圆满完成解答的.
题:将边长为
的正方形硬纸片(如图1)的四个角裁去四个相同的小正方形后,折成如图2的无盖长方体小纸盒,求纸盒容积的最大值.
,则纸盒容积
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71c081a56a12c5d11c9b4f31008a65ec.png)
当且仅当
,即
时取等号.所以纸金的容积取得最大值
.在求
的最大值中,用均值不等式求最值时,遵循“一正二定三相等”的规则.你也可以将
变形为
求解.
你还可以设纸盒的底面边长为
,高为
,则
,则纸盒容积
.
当且仅当
,即
,
时取等号,所以纸盒的容积取得最大值
.
材料2.《数学必修二》第八章8.3节习题8.3设置了如下第4题:
如图1,圆锥的底面直径和高均为
,过
的中点
作平行于底面的截面,以该截面为底的面挖去一个圆柱,求剩下几何体的表面积和体积.我们称圆柱为圆锥的内接圆柱.
根据材料1与材料2完成下列问题.
如图2,底面直径和高均为
的圆锥有一个底面半径为
,高为
的内接圆柱.
与
的关系式;
(2)求圆柱侧面积的最大值;
(3)求圆柱体积的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67ca5fd57c2c2fcc3c7a574fdd1467d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/689f982af451283289255c87593ec338.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f22fec5a381ae8aca93d876e54c79de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67ca5fd57c2c2fcc3c7a574fdd1467d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cec12441802f71e803efaf2c62ee588.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d936ea1443a8c881633d5e04fdd3434.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44acc0ee22dc4b7750e8be825e7c1355.png)
题:将边长为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/689ff84e2d7f52c7446ef789a54557da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4e3c92be4b3f494e7d03c67819632c0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71c081a56a12c5d11c9b4f31008a65ec.png)
当且仅当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efaf86a31a17f80098a020b74d5282bc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/707ea658f3a9359f5740d5aab48f7948.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b50995580ef9cbc240041c2f8d00d79d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be54e84508decfcce6d2fcbe6c8c1a92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dbb2757026c0f75d4f1ea56349b177b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab79a858ff360048fb4f1f7784cbfe8d.png)
你还可以设纸盒的底面边长为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/493dbbbcf8aecaf1b586774ad7846f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/db442d96d27b4c73a3dc684756b7a0b2.png)
当且仅当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3527a89afa5fbd67781a204d3954a02e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36e15cbd7c42d7b15d7ba8d2b28ab8df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03837b3769eda7f0d3804cc5ad4a6d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b50995580ef9cbc240041c2f8d00d79d.png)
材料2.《数学必修二》第八章8.3节习题8.3设置了如下第4题:
如图1,圆锥的底面直径和高均为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef49a3ca580a144cc65a609c167facc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
根据材料1与材料2完成下列问题.
如图2,底面直径和高均为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dd6f4250ca6b1b9bce234a01f00d44d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aa0df7f1e45f9de29e802c7f19a4f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aa0df7f1e45f9de29e802c7f19a4f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
(2)求圆柱侧面积的最大值;
(3)求圆柱体积的最大值.
您最近一年使用:0次
名校
解题方法
2 . 为了求一个棱长为
的正四面体的体积,某同学设计如下解法.
解:构造一个棱长为1的正方体,如图1:则四面体
为棱长是
的正四面体,且有
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/16/6db5d8bf-a942-4eb1-b74e-0d41be5b6734.png?resizew=583)
(1)类似此解法,如图2,一个相对棱长都相等的四面体,其三组棱长分别为
,
,
,求此四面体的体积;
(2)对棱分别相等的四面体
中,
,
,
.求证:这个四面体的四个面都是锐角三角形;
(3)有4条长为2的线段和2条长为
的线段,用这6条线段作为棱且长度为
的线段不相邻,构成一个三棱锥,问
为何值时,构成三棱锥体积最大,最大值为多少?
[参考公式:三元均值不等式
及变形
,当且仅当
时取得等号]
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
解:构造一个棱长为1的正方体,如图1:则四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68ac02c2f91cadb1e328bc6ab9b9c491.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6f878ffcff2ca25a434cbeea7d5c841.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/16/6db5d8bf-a942-4eb1-b74e-0d41be5b6734.png?resizew=583)
(1)类似此解法,如图2,一个相对棱长都相等的四面体,其三组棱长分别为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2967337e3fcb228dded64ab0c41a17e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/50690dab38f4512eb72e18b7f86cf6f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4056761b8f826eeb6ad8c9a151d3c9c.png)
(2)对棱分别相等的四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7de966c316db1013defc56372fcf814e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8d2530e7023b2345c651e8f53629ff1.png)
(3)有4条长为2的线段和2条长为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
[参考公式:三元均值不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ffb6b373d2e672bb2afc8de547861a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4849ff71159df2bb9099b26065d81e1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44acc0ee22dc4b7750e8be825e7c1355.png)
您最近一年使用:0次
2021-07-15更新
|
814次组卷
|
2卷引用:重庆市西南大学附属中学2020-2021学年高一下学期期末数学试题
3 . 我国古代数学著作《九章算术》中记载:斜解立方,得两堑堵.其意思是:一个长方体沿对角面一分为二,得到两个一模一样的堑堵.如图,在长方体
中,
,
,
,将长方体
沿平面
一分为二,得到堑堵
,下列结论正确的序号为______ .
①点C到平面
的距离等于
;
②
与平面
所成角的正弦值为
;
③堑堵
外接球的表面积为
;
④堑堵
没有内切球.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efc6e4b936d7a800e839a30c3839574d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e65a3e478bb87d094e3a0af30dd10ae8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f3e58edd1f900ca82bb2a3058293f52.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/679748eab882a6be0fefd2cc300349a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/4/2/203cf047-3c7e-43ff-9a8e-fb0157d5f7d4.png?resizew=233)
①点C到平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/679748eab882a6be0fefd2cc300349a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81365a3726621b6557bd26f3a1a51cae.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/588eb9393564a33552c4b2e8de837ca5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15a24acb11fac4bcf6a86e3e9223a48b.png)
③堑堵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f08a01aed02ce1eaf1aaefaa0342b7ad.png)
④堑堵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b5b14d74bdf9ed7c45b2e754b7ccc4f.png)
您最近一年使用:0次
名校
解题方法
4 . 我国古代劳动人民在筑城、筑堤、挖沟、挖渠、建仓、建囤等工程中,积累了丰富的经验,总结出了一套有关体积、容积计算的方法,这些方法以实际问题的形式被收入我国古代数学名著《九章算术》中.《九章算术
商功》:“斜解立方,得两堑堵.斜解堑堵,其一为阳马,一为鳖臑.阳马居二,鳖臑居一,不易之率也.合两鳖臑三而一,验之以棊,其形露矣.”下图解释了这段话中由一个长方体,得到“堑堵”、“阳马”、“鳖臑”的过程.已知如图堑堵的棱长
,则鳖臑的外接球的体积为_________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e85bda46cc51c938224d9165301e3896.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/814883ab9eddcfa676c7413a74d62d9d.png)
![](https://img.xkw.com/dksih/QBM/2020/6/30/2495938048925696/2497171298246656/STEM/d9960f0034d24382a856916070dea1da.png?resizew=339)
您最近一年使用:0次
5 . 我国古代劳动人民在筑城、筑堤、挖沟、挖渠、建仓、建囤等工程中,积累了丰富的经验,总结出了一套有关体积、容积计算的方法,这些方法以实际问题的形式被收入我国古代数学名著《九章算术》中.《九章算术·商功》:“斜解立方,得两堑堵.斜解堑堵,其一为阳马,一为鳖臑.阳马居二,鳖臑居一,不易之率也.合两鳖臑三而一,验之以棊,其形露矣.”下图解释了这段话中由一个长方体,得到“堑堵”、“阳马”、“鳖臑”的过程.已知堑堵的内切球(与各面均相切 )直径 为1,则鳖臑的体积最小值为( )
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/23/d9034dd9-60ab-458f-9255-214872f23dc0.png?resizew=485)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/23/d9034dd9-60ab-458f-9255-214872f23dc0.png?resizew=485)
A.![]() | B.![]() | C.![]() | D.![]() |
您最近一年使用:0次
6 . 《九章算术商功》:“斜解立方,得两堑堵.斜解堑堵,其一为阳马,一为鳖臑.”其中,阳马是底面为矩形,且有一条侧棱与底面垂直的四棱锥.如图,在阳马
中,侧棱PA垂直于底面ABCD,且
,则该阳马的外接球的表面积等于______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be5d1bfdfd201164a16ee8cc4644a984.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/15/80b9dad1-df02-4f7a-81bc-3df40603215e.png?resizew=121)
您最近一年使用:0次
7 . 《九章算术·商功》:“斜解立方,得两壍堵(qiàn dǔ).斜解壍堵,其一为阳马,一为鳖臑(biē nào).阳马居二,鳖臑居一,不易之率也.”文中所述可用下图表示:
![](https://img.xkw.com/dksih/QBM/2022/1/14/2894203289747456/2895176848777216/STEM/8c0d64b8-e798-4905-a031-747276d8fa23.png?resizew=384)
则几何体“鳖臑”的四个面中,直角三角形的个数为_______ ;若上图中的“立方”是棱长为1的正方体,则
的中点到直线
的距离等于________ .
![](https://img.xkw.com/dksih/QBM/2022/1/14/2894203289747456/2895176848777216/STEM/8c0d64b8-e798-4905-a031-747276d8fa23.png?resizew=384)
则几何体“鳖臑”的四个面中,直角三角形的个数为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d8772aa893a9c1d40f714cb25701701.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e539f26ed5e0b20ff7220559324869a4.png)
您最近一年使用:0次
8 . 中国古代数学名著《九章算术•商功》中,阐述:“斜解立方,得两堵.斜解壍堵,一为鳖臑.阳马居二,鳖臑居一”,
平面ABC,
,PA=AB=BC=4,则PB与AC所成的角等于______ ;PC与AB之间的距离等于______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/080db3af81b29ed10144a1c2e2a4fb8a.png)
![](https://img.xkw.com/dksih/QBM/2021/10/21/2834324322140160/2834895242723328/STEM/03c7391e49664728926e4b1399819c8e.png?resizew=128)
您最近一年使用:0次
名校
解题方法
9 . 《九章算术·商功》:“斜解立方,得两堑(qiàn)堵(dǔ).斜解堑堵,其一为阳马,一为鳖(biē)臑(nào).阳马居二,鳖臑居一,不易之率也.合两鳖臑三而一,验之以棊,其形露矣.”刘徽注:“此术臑者,背节也,或曰半阳马,其形有似鳖肘,故以名云·中破阳马,得两鳖臑,鳖臑之起数,数同而实据半,故云六而一即得.”阳马和鳖臑是我国古代对一些特殊锥体的称谓,取一长方体,按下图斜割一分为二,得两个一模一样的三棱柱,称为堑堵,再沿堑堵的一顶点与相对的棱剖开,得四棱锥和三棱锥各一个,以矩形为底,另有一棱与底面垂直的四棱锥,称为阳马,余下的三棱锥是由四个直角三角形组成的四面体,称为鳖臑.
:
①在右图中,求三棱锥
的高.
②求三棱锥
外接球的表面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c8cf5d11389d101e9ebf87764d0f8dd.png)
①在右图中,求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac7a3e0ef4980cc0ca102f733d357263.png)
②求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac7a3e0ef4980cc0ca102f733d357263.png)
您最近一年使用:0次
名校
10 . 如图,在平行六面体
中,
,
,
.用向量法 解下列问题:
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/30/5cb11c55-bc0f-4bea-85db-1259fb30f49c.png?resizew=165)
(1)求
长度;
(2)求证:
;
(3)若点M,N分别在直线
和
上运动,当
且
时(MN为公垂线段,这样的MN只有一条),求MN的长度.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3da8c338342e38c9aa3f274c053fd5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/067613594cca07e73993d85045e8964f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d262480ffb55b7617f44b63f130c154a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92535536bd3c2761724fd058427f95a8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/30/5cb11c55-bc0f-4bea-85db-1259fb30f49c.png?resizew=165)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6eb97aff0960e2640314888a38e7169c.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b219a74a1ce5a2b22c36d8de1e21ff91.png)
(3)若点M,N分别在直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82b25f3ea33cc08b1e2a0d9c3a9dccaf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6eb97aff0960e2640314888a38e7169c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df93277710b49a14d6ff1b9d5e99260c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/722ba1f4d15c9bf91ef3de85202e9406.png)
您最近一年使用:0次