名校
1 . 利用反证法证明“已知
,求证:
中,至少有一个数大于20.”时,首先要假设结论不对,即就是要假设( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b7267291073b77eab69d5d01383c045d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/874781ab5711bff6ee8c9cbad5b3b3dc.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
您最近一年使用:0次
2021-09-04更新
|
96次组卷
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2卷引用:陕西省咸阳市武功县普集高中2021-2022学年高二下学期第一次月考理科数学试题
解题方法
2 . 已知
,求证
.某同学解这道题时,注意到结论中的三个量
,
,
.由已知条件得到
,
,
.进一步发现三者的关系:
.又观察左边式子的结构发现就是两个数的倒数和,从而联想到以前做过的题目“已知
,
,求证
”,类比其解法得到题目的解法:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f60d4d44e161c4c3e151ad73024a8228.png)
,当且仅当
时取等号.所以
.求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/497d269c30eec393e3f0e877ddbe2983.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/323f4e181b418a66cc36d75e0f8da126.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9f2416d1f75a45a314331146550832e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9db8d3facff8f90f28a936fc5b3ab878.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ea712984ea5017140e20bee226fd5af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/481ee0d1e39e92a4732eea90225eb94c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/936553b69099e03189581a42a5c1d8aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d6e90787c63ca5b5f1a45e0f6e85aaa1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0c05be59bdd7874fd8e9ee5ba5b17f4.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/86546d8c56d9c72822cc2c834e240ad1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f60d4d44e161c4c3e151ad73024a8228.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55eb4703dc394b53fef7d12030c470d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/914c9d4dc14490413e77f6262d2a7aa9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/323f4e181b418a66cc36d75e0f8da126.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81e743594b98ac2006344494dddfb345.png)
您最近一年使用:0次
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3 . 用反证法证明命题“对任意
,都有
时,应首先“假设___________ ”,再推出矛盾,从而说明假设不能成立,原命题为真命题.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a37a59558292ad6b3d0978bfd7484990.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/397220a2025730da198a1ee02fef1b76.png)
您最近一年使用:0次
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4 . 下列语句是命题的是( )
A.二次函数的图象太美啦! | B.这是一棵大树 |
C.求证:![]() | D.3比5大 |
您最近一年使用:0次
5 . 余弦定理是揭示三角形边角关系的重要定理,也是在勾股定理的基础上,增加了角度要素而成.而对三角形的边赋予方向,这些边就成了向量,向量与三角形的知识有着高度的结合.已知
,
,
分别为
内角
,
,
的对边:
(1)请用向量方法证明余弦定理
;
(2)若
,其中
为
边上的中线,求
的长度.
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.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)
(1)请用向量方法证明余弦定理
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34369422d71dd95c61cdd1b8245d7b6c.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48897a577999a24e15e8645e7b23e592.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
您最近一年使用:0次
2023-06-11更新
|
630次组卷
|
4卷引用:江苏省苏州园二2023-2024学年高一下学期3月月考数学试题
解题方法
6 . 如图所示圆锥
中,
为底面的直径.
分别为母线
与
的中点,点
是底面圆周上一点,若
,
,圆锥的高为
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/16/7e6c7737-8e52-4b2b-af91-453629c38943.png?resizew=160)
(1)求圆锥的侧面积
;
(2)求证:
与
是异面直线,并求其所成角的大小
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f9654c9824b84dce1f840e3414c47ddc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cdebc1592efdbdf58b9b0dd9ee725c32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ff1c07d3ab5f594be5fffe13ebaaccb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01961669cd597f61fa48e9853d678bb8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/16/7e6c7737-8e52-4b2b-af91-453629c38943.png?resizew=160)
(1)求圆锥的侧面积
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
您最近一年使用:0次
2022-12-15更新
|
859次组卷
|
2卷引用:上海市普陀区桃浦中学2022-2023学年高二上学期10月月考数学试题
名校
7 . 如图,在
中,
为
边上一点,且
.
,求实数
、
的值;
(2)若
,求
的值;
(3)设点
满足
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3fe95f656b98b53f71a9d72bf0c9a4b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d71cde9bbb9c8fa969e04f8d0254eba7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/810633059a470392035aa375dfc20fd7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e06ca53803f042a5eca99f56a70f05e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c77037587e3cc14dec8d74541341cbc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7a66e27ef92fcc51530e54533e23973.png)
(3)设点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6cfeef6dbc266f8ca53f78e7833e82d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29dfd8c22112c99c63890e79ecffa94f.png)
您最近一年使用:0次
2022-12-09更新
|
1805次组卷
|
11卷引用:江苏省盐城市东台创新高级中学2022-2023学年高一下学期2月月检测数学试题
江苏省盐城市东台创新高级中学2022-2023学年高一下学期2月月检测数学试题广东省深圳市龙华外国语高级中学2023-2024学年高一下学期第一次段考数学试卷上海市曹杨第二中学2021-2022学年高一下学期期末数学试题第9章《平面向量》单元达标高分突破必刷卷(基础版)第八章 向量的数量积与三角恒等变换(A卷·基础通关练)-【单元测试】2022-2023学年高一数学分层训练AB卷(人教B版2019必修第三册)第六章 平面向量及其应用(A卷·基础提升练)-【单元测试】2022-2023学年高一数学分层训练AB卷(人教A版2019必修第二册)(已下线)专题6.14 平面向量及其应用全章综合测试卷(基础篇)-2022-2023学年高一数学举一反三系列(人教A版2019必修第二册)福建省宁德市福安市阳光国际集团福建区域联考2022-2023学年高一下学期期中数学试题单元测试A卷——第六章?平面向量及其应用(已下线)上海市高一下学期期末真题必刷03-期末考点大串讲(沪教版2020必修二)辽宁省大连市滨城高中联盟2023-2024学年高一下学期5月期中考试数学试题
名校
8 . 已知实数
满足
,则下列结论的证明更适合用反证法的是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b45900deae0489e87fe448948e8091c4.png)
A.证明![]() | B.证明![]() |
C.证明![]() | D.证明![]() |
您最近一年使用:0次
2021-08-30更新
|
121次组卷
|
5卷引用:河南省郑州市第四高级中学2021-2022学年高二下学期第三次月考(期末模拟)理科数学试题