23-24高二下·全国·课前预习
解题方法
1 . 分类变量
(1)分类变量:为了方便,用一种特殊的随机变量,以区别不同的现象或性质,这类随机变量称为分类变量.
(2)取值:分类变量的取值可以用________ 表示.
(3)范围:本节主要讨论取值于
的分类变量的关联性问题.
(4)判断分类变量之间关系的方法
①利用数形结合思想,借助等高堆积条形图来判断两个分类变量是否相关是判断变量是否相关的常见方法;
②在等高堆积条形图中,
与
相差越大,两个分类变量有关系的可能性就越大.
(1)分类变量:为了方便,用一种特殊的随机变量,以区别不同的现象或性质,这类随机变量称为分类变量.
(2)取值:分类变量的取值可以用
(3)范围:本节主要讨论取值于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8b2be1b0b6bea70d4e64894f1009359.png)
(4)判断分类变量之间关系的方法
①利用数形结合思想,借助等高堆积条形图来判断两个分类变量是否相关是判断变量是否相关的常见方法;
②在等高堆积条形图中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aefd09f80733a8c98bd8c51905d15fe5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85b65a2ec5d67fb0c2cc1acc45fe0c5a.png)
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2024·全国·模拟预测
解题方法
2 . 在解决问题“已知正实数
满足
,求
的取值范围”时,可通过重新组合,利用基本不等式构造关于
的不等式,通过解不等式求范围.具体解答如下:
由
,得
,即
,解得
的取值范围是
.
请参考上述方法,求解以下问题:
已知正实数
满足
,则
的取值范围是______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb975603433961a27ff01c734d39575f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
由
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d14a76fbd7733394b3a7a8c7508ae8f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09a2ebb75f6dc5ba596a98ccbc2bb9be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef066cf9a851361e923ed40c97b842.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f29d5f376c75c41ae6af0c8a8565449.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eed05aa46ec16ee8f98272565d2a2ed9.png)
请参考上述方法,求解以下问题:
已知正实数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb975603433961a27ff01c734d39575f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4e7bf9200b351a259ddfc6c0266129d.png)
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2023高二·全国·专题练习
3 . 两个向量的夹角
(1)定义:已知两个非零向量
,作
,则
叫做
与
的夹角;
(2)范围:夹角
的取值范围是_________ .
①当
与
同向时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
_______ ;②反向时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
_____ ;③当
与
垂直时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
_______ ,并记作
.
(1)定义:已知两个非零向量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8e8b95a61af300412fc65f846089028.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cefb3de8805e7febdf23b4e959d9711.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb7e00f8bacce4d649b535449f04568c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ae98586d80f892771c90ab39eaced90.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee437e6ff470c2f67b8429f57b90ae37.png)
(2)范围:夹角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
①当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ae98586d80f892771c90ab39eaced90.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee437e6ff470c2f67b8429f57b90ae37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ae98586d80f892771c90ab39eaced90.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee437e6ff470c2f67b8429f57b90ae37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b657cfa91b6394e4b00fa385a2c0149.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8bf21fef3026cfe445a855c94cab5c84.png)
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