名校
解题方法
1 . 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:上海市嘉定区第一中学2021-2022学年高二上学期期末数学试题
名校
解题方法
2 . 有一圆柱形的无盖杯子,他的内表面积是
.
(1)试用解析式将杯子的容积
表示成底面半径
的函数;
(2)定理:若
,则
,当且仅当
时等号成立.
阅读下列解题过程:求函数
的最大值.
解:
,当且仅当
,即
时等号成立,所以
时,
的最大值为
.
问:当杯子的底面半径为多少时,杯子的容积最大,最大容积是多少?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b12d5b15f6979cd665d54fd17341fc2f.png)
(1)试用解析式将杯子的容积
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04b785a4b6636ed1f145ed8f7e3a0fef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5be6e964c405a9cdf6623f9219898fd3.png)
(2)定理:若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c0c9fd7b50fc20cc3e7c0bd4442c306.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/162cd9270205b4e891f7e806abe01bf5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44acc0ee22dc4b7750e8be825e7c1355.png)
阅读下列解题过程:求函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/896cf6a3fcde580b4cd78431ba255d0f.png)
解:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68661d53ba9a388797dc9a42595a593d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25359e135f750694a9103837dbc9a291.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/280878aa2e6d5580178cc6c99229b9ed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/280878aa2e6d5580178cc6c99229b9ed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/738bc12c4d44438814ce6f606fda695a.png)
问:当杯子的底面半径为多少时,杯子的容积最大,最大容积是多少?
您最近一年使用:0次
名校
解题方法
3 . 已知函数
.
(1)解不等式
;
(2)设
均为实数,当
时,
的最大值为1,且满足此条件的任意实数
及
的值,使得关于
的不等式
恒成立,求
的取值范围;
(3)设
为实数,若关于
的方程
恰有两个不相等的实数根
,且
,试将
表示为关于
的函数,并写出此函数的定义域.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14c056eb5efd19642d29636242f2e5e0.png)
(1)解不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39d4bdc091d164863ffabe2a60c7e847.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef3e9eb0c4bd9c899886668229c4c947.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b9849dc6798e2c2ec12730b92117e77.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a863acb0ba30d483b216c4409b8b20f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
(3)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6baa1c342eccdee55f4b91793bfe2d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ce7ae90d808f05e86ea063238e4b2f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/26d8dafc71b106f39f4e15442220897b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78eb25c4cd80bc4cf705a3dd92a04f78.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
您最近一年使用:0次
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6卷引用:上海市普陀区2021届高三上学期一模数学试题
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