名校
1 . 已知
为实数.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/874781ab5711bff6ee8c9cbad5b3b3dc.png)
![](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
名校
2 . 给定不共面的4点,作过其中3个点的平面,所有4个这样的平面围成的几何体称为四面体(如图所示),预先给定的4个点称为四面体的顶点,2个顶点的连线称为四面体的棱,3个顶点所确定的三角形称为四面体的面.求证:四面体中任何一对不共顶点的棱所在的直线一定是异面直线.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/1/7591e2f1-42ef-474b-ae38-6e946dfe7429.png?resizew=151)
(1)请你用异面直线判定定理证明该结论;
(2)请你用反证法证明该结论.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/1/7591e2f1-42ef-474b-ae38-6e946dfe7429.png?resizew=151)
(1)请你用异面直线判定定理证明该结论;
(2)请你用反证法证明该结论.
您最近一年使用:0次
3 . 已知实数
,
,
.
(1)若
,求
的值;
(2)求证:
;
(3)用反证法证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce613eaa5df46a50174085ef5d1087fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/751e274e9107d780c39ba9c49d6daefb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f9223bc24df8d429d743692fff7c06.png)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/919f4bbc4dd7aef5314ac0e183872d6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9f2416d1f75a45a314331146550832e.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09b469b34530be2e760b144b8a571506.png)
(3)用反证法证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f75807858b7804a1ad2039c41f323a18.png)
您最近一年使用:0次
名校
4 . 若集合A具有以下性质:①
,
;②若x、
,则
,且
时,
.则称集合A是“好集”.
(1)分别判断集合
是否是“好集”,并说明理由;
(2)设集合A是“好集”,求证:若x、
,则
;
(3)对任意的一个“好集”A,证明:若x、
,则必有
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2faf3937abcb6a59071c17bc6bb10f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35a2410ce34b36954ed4923e600d42f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e63c91626ffa91e590925e6f206c3c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c46de01c5104b9112a688df37eadb000.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38f0e9c04402a0ffdaa25c3e3c82c7dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cd77104cc745d1e0e262122da34482d.png)
(1)分别判断集合
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc51474b54120493b300a14e566cbc0e.png)
(2)设集合A是“好集”,求证:若x、
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e63c91626ffa91e590925e6f206c3c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/957d41dbe52b49c3a7339e3519a3fe84.png)
(3)对任意的一个“好集”A,证明:若x、
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e63c91626ffa91e590925e6f206c3c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09db4828342fb0a79e0ea8d132b76e6f.png)
您最近一年使用:0次
5 . 在四面体ABCD中,AB=BD=CD=1,AB⊥平面BCD,CD⊥BD,点M为AD上动点,连结BM,CM,如图.
![](https://img.xkw.com/dksih/QBM/2021/11/8/2846676231233536/2848045236518912/STEM/2e611f1c7e2a4701a5601e2c9023264e.png?resizew=227)
(1)求证:BM⊥CD;
(2)若AM=2MD,求二面角M﹣BC﹣D的余弦值;
(3)是否存在一个球,使得四面体ABCD的顶点都在此球的球面上?若存在,确定球心的位置并证明;若不存在,请说明理由.
![](https://img.xkw.com/dksih/QBM/2021/11/8/2846676231233536/2848045236518912/STEM/2e611f1c7e2a4701a5601e2c9023264e.png?resizew=227)
(1)求证:BM⊥CD;
(2)若AM=2MD,求二面角M﹣BC﹣D的余弦值;
(3)是否存在一个球,使得四面体ABCD的顶点都在此球的球面上?若存在,确定球心的位置并证明;若不存在,请说明理由.
您最近一年使用:0次
2020高一·上海·专题练习
解题方法
6 . 求证:
是非奇非偶函数,证明如下:
,这种证法正确吗?若正确,说明理由;若不正确,请给出正确的证法.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c395237799431ccbd691c17d5c78ac3e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca396931119b281c453a851379538961.png)
您最近一年使用:0次
7 . 在
中,若
,
.
(1)若D为BC上的点,且
,求证:
;
(2)若P、Q是线段BC的三等分点,求证:
;
(3)若P、Q、S是线段BC的四等分点,求证:
;
(4)如果
、
、
、…、
是线段BC的
等分点,你能得到什么结论?不必证明.(已知
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f550d33a4813211cbed34fb6823ac66d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21476d039b3ccdc18abbb612e0680f97.png)
(1)若D为BC上的点,且
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/774a62a279de4423bb92740126597fbb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1e32292ee128056a2331c59dfecb9b5.png)
(2)若P、Q是线段BC的三等分点,求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5419e975f6927776949a2799f62f2f20.png)
(3)若P、Q、S是线段BC的四等分点,求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17faf80f1773da08926c7b501c502fc9.png)
(4)如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd3b9e816b14051f785aa5aae72b8eed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04b56e44e4f0424a2b7a45567120a2e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94ea50db79b18d8700cfa2559ff5e2d1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ec7ec8d43a898c8333b2e04d656fd79.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8da64b6691477e8662d0519808d6f47.png)
您最近一年使用:0次
2021-03-25更新
|
215次组卷
|
2卷引用:沪教版(2020) 必修第二册 同步跟踪练习 第8章 平面向量 8.1~8.2 阶段综合训练
名校
解题方法
8 . 柯西不等式具体表述如下:对任意实数
,
,
和
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13423c094861baf4b759b7f3d8c3c226.png)
,
都有
,当且仅当
时取等号.
(1)请用柯西不等式证明:对任意正实数
,
,
,
,不等式
成立,(并指出等号成立条件)
(2)请用柯西不等式证明:对任意正实数
,
,
,
,且
,求证:
(并写出等号成立条件).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e88093a749c0d46e0ee931ecfaff925.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09356b015bc795d6d54cd3ba4078b265.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b715e7842b95f654f16056a7c7f2abe9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13423c094861baf4b759b7f3d8c3c226.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9c254ae1c29768fed8c7f9a14d52395.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de74ebc1d7d0ef4f23c30ecdddbb9a7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9c54ff21406dc68cdab0d21351daf51.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0b90c1b5ccde843b2e8fea459376247.png)
(1)请用柯西不等式证明:对任意正实数
![](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/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29574517e0bd98aa055ee15120f8fff1.png)
(2)请用柯西不等式证明:对任意正实数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c814128ea2139e33db94ea590e7c2223.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aec19b68e3add9d5bfcc6269a1855b87.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daa5e9bd516f6282483b92cfe6074623.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3282e5fde4ae53fcb1bb072a685304c9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b16ad49f62d7362441e3b92efe7f87d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8b3d6d2614a5cdbddc5964194a1a925.png)
您最近一年使用:0次
9 . 证明不等式
(1)已知
,证明:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83d83e848867829e2ac31d60bb9ef902.png)
(2)设
,求证:
(1)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf04fe8895c10624636a815d3d752975.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83d83e848867829e2ac31d60bb9ef902.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/044b0aa13a404dc0b94df51707adbf27.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78f7c0a9a5ea5a40df5f753deba43188.png)
您最近一年使用:0次
2020-12-02更新
|
318次组卷
|
6卷引用:大题能力提升考前必做30题-2020-2021学年高一数学期末考试高分直通车(沪教版2020,必修一)
(已下线)大题能力提升考前必做30题-2020-2021学年高一数学期末考试高分直通车(沪教版2020,必修一)江苏省淮安市阳光学校2020-2021学年高一上学期第二次月考数学试题(已下线)第二单元 (综合培优)一元二次函数与方程、不等式 B卷-【双基双测】2021-2022学年高一数学同步单元AB卷(人教A版2019必修第一册)(已下线)2.3平均值不等式证明(第1课时)沪教版(2020) 必修第一册 精准辅导 第2章 2.3(2) 平均值不等式及其应用(2)(已下线)江苏省常州市金坛区2023-2024学年高一上学期期中质量调研数学试卷
名校
10 . 用反证法证明“设
,求证
”时,第一步的假设是______________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/127a0d8c1c7d15ed40ec4b8bca0ebdf6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/485a2d99320384a0857b00ce9ab9e990.png)
您最近一年使用:0次
2020-03-20更新
|
475次组卷
|
7卷引用:上海市浦东新区2021-2022学年高一上学期期末数学试题