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.
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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)
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2021-07-15更新
|
814次组卷
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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
解题方法
3 . (1)解关于x的不等式
;
(2)设
,求函数
的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96ed3227679cfb24a9f0d0c532ba308a.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fecaefda8567646f10d76668293d845.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20efa2b5a009ce729dd36da7f33458d8.png)
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解题方法
4 . 下列命题错误的是( )
A.“![]() ![]() |
B.已知![]() ![]() ![]() ![]() |
C.命题p:![]() ![]() ![]() ![]() ![]() |
D.不等式![]() ![]() ![]() ![]() |
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解题方法
5 . 解下列问题:
(1)已知
,
,且
,求
的最大值;
(2)已知
,求函数
的最大值;
(3)若正数
,
满足
,求
的最小值.
(1)已知
![](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/d676a58fa4d7c4e8985b85c033495c7a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/18f0281e6bbdbe08beeccb55adf84536.png)
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3697ec54c1e6516bb71f5b2431d1870.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3dcb6ea431bc38718c156d3866f83bf1.png)
(3)若正数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d57df333b2783a9d7eacfa8cf6c81c42.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c3836619ba47499fca6df4e5182da9d.png)
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2卷引用:湖南省长沙市实验中学2023-2024学年高一上学期第一阶段性检测数学试题
名校
解题方法
6 . 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?
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解题方法
7 . 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)
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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
上海市普陀区2021届高三上学期一模数学试题(已下线)课时13 函数的基本性质-2022年高考数学一轮复习小题多维练(上海专用)(已下线)考向03 函数及其性质-备战2022年高考数学一轮复习考点微专题(上海专用)上海市奉贤中学2022届高三上学期开学考数学试题上海市川沙中学2022届高三上学期第一次月考数学试题上海市实验学校2022-2023学年高一上学期期末数学试题
解题方法
8 . 解下列各题:
(1)已知
,求
的范围:
(2)已知
,求
的最大值.
(1)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb63178fcd8cb8cde9e4f3fd41c971a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d9c824503141db5205016e7d6563a414.png)
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e93d618bc1724acec86edf556320b99.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0380043fd4019375c3afad295623fce9.png)
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9 . 在
中,角
、
、
所对的边分别为
、
、
.
(1)若
,
,求
面积的最大值;
(2)若
,试判断
的形状.
(3)结合解答第(2)问请你总结一下在解三角形中判断三角形的形状的方法.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](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/071a7e733d466949ac935b4b8ee8d183.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6de1d395e6c48c0676a1488a299479d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e38f550e95b2950f91e8ec1798b94109.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3b4c796d2023364f72b1a6c3e7079c3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
(3)结合解答第(2)问请你总结一下在解三角形中判断三角形的形状的方法.
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10 . 选修4-5 不等式选讲
已知函数
.
(1)解不等式![](https://staticzujuan.xkw.com/quesimg/Upload/formula/881f24963a864773a54b3f2f01b6158a.png)
(2)若函数
的最小值为
,且
,
,求
的最大值.
已知函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00af88112428d42b13ad4bafefdc2f1c.png)
(1)解不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/881f24963a864773a54b3f2f01b6158a.png)
(2)若函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d479a86a1711709b2d100fe4daf3e7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aedb503f6f65771e3d5c96c769016f80.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/228032ab3d2ee82e5ecc9413aa13b3dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d993cf0a090de3b01f1dda52c6fdc9f.png)
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