名校
1 . 现代社会对破译密码的难度要求越来越高,有一处密码把英文的明文(真实名)按字母分解,其中英文a,b,c……,z这26个字母,依次对应1,2,3……,26这26个正整数.(见下表)
用如下变换公式:
将明文转换成密码.如
.即h变成q;再如:
,即y变成m;按上述变换规则,若将明文译成的密码是gano,那么原来的明文是______________ .
a | b | c | d | e | f | g | h | i | j | k | l | m |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
n | o | p | q | r | s | t | u | v | w | x | y | z |
14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4872ec3fbe9da9c42ef5accdee71a78.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8695029f51332295a5e8a8e11904e7be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/590413d8b51ff7cd5a237cee3fde25bf.png)
您最近一年使用:0次
名校
解题方法
2 . 对于正项数列
,定义
为数列
的“匀称”值.
(1)若当数列
的“匀称”值
,求数列
的通项公式;
(2)若当数列
的“匀称”值
,设
,求数列
的前
项和
及
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1a640d536ca58f9687b6ed44bf7aae8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(1)若当数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dbc4d29fb7ed6b0459b28efa354355b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若当数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e309e4d31afddeecac92b4dce9c13d0c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9096e9a72d6dbdbcf1236d3870a275f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2d51f9147b8265c0276c1f2c2659197.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b9a0d7150fb24be3e28ef7f0e18be93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b9a0d7150fb24be3e28ef7f0e18be93.png)
您最近一年使用:0次
名校
3 . 某地区为了了解本年度数学竞赛成绩情况,从中随机抽取了
个学生的分数作为样本进行统计,按照
,
,
,
,
的分组作出频率分布直方图如图所示,已知得分在
的频数为20,且分数在70分及以上的频数为27.
![](https://img.xkw.com/dksih/QBM/2020/2/15/2399561905553408/2399766145744896/STEM/919f660192b04c14ae65745212cf4f97.png?resizew=216)
(1)求样本容量
以及
,
的值;
(2)在选取的样本中,从竞赛成绩在80分以上(含80分)的学生中随机抽取2名学生,求所抽取的2名学生中恰有一人得分在
内的概率.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/627a86a6ccc6968f95c9e26db5c4b80d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8826cd3a88388c3896b1e429fabd437f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f58d9a123e465dace224231f54ee94e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a40cf767fd2a684f2f1ed9216836792.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13a0dc3b0349c53d7bf36dfe97958cea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f58d9a123e465dace224231f54ee94e8.png)
![](https://img.xkw.com/dksih/QBM/2020/2/15/2399561905553408/2399766145744896/STEM/919f660192b04c14ae65745212cf4f97.png?resizew=216)
(1)求样本容量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
(2)在选取的样本中,从竞赛成绩在80分以上(含80分)的学生中随机抽取2名学生,求所抽取的2名学生中恰有一人得分在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a40cf767fd2a684f2f1ed9216836792.png)
您最近一年使用:0次
名校
解题方法
4 . 在
中,角
,
,
所对的边分别为
,
,
,且
.
(1)求证:
;
(2)若
,求
.
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f296989add06c4bc2207a20b0746e533.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ff7989c371fc6dd1627bdb88fcb917d.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7b9446d7b31f0d6e044cf99deeb20aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5201fc26d013f6fb889933c0e32f5c53.png)
您最近一年使用:0次
5 . 已知等差数列
中,首项
,
.
(1)求
的通项公式;
(2)若等比数列
满足
,
,求
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d3c41de954935a705c1452fa3b36e0e.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若等比数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4995fa0403e013d888c0935ebfe15024.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2c16771a3e64b8f084ee6cf89a02705.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
您最近一年使用:0次
6 . 在
中,角
,
,
所对的边分别为
,
,
,且
.
(1)求角
的值;
(2)若
,
,求
的面积.
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ac63ef27877b3e4dc451e5aedcf6f8e.png)
(1)求角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/036b23c94e305faaa1283996edc5b30c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ef9e1e927934f8ae7a2a60a18cfc763.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
您最近一年使用:0次
名校
解题方法
7 . 设单位向量
,
的夹角是
,且
,
.
(1)计算
;
(2)计算
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8315ec34019d719771152be2252106e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3cf39ca3294f5520518dd4f1c0609876.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d88591679796c52024d11c4de641bdb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61a3a2afa12f81952a3a5a9e287773c0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e3e1577b7a6a3da68ee1941e54dd97e.png)
(1)计算
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a560b8ff794c12dc8d194bcd2e3f3554.png)
(2)计算
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ca7702985467337a01e955f92622f53.png)
您最近一年使用:0次
名校
解题方法
8 .
中角
,
,
的对边分别是
,
,
,若
,且
,则
的面积最大值为______ .
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb427583b0ba66812f6febae2f5f8162.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcb5bac75f36bb1dc5c8190d4dbe681d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
您最近一年使用:0次
名校
9 . 在等差数列
中,
,
,则前
项和为
的最大值为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06ae16720511620cd8cbb904f9f6be6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f01828ef9f7dec29057350e75a6fe4b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
您最近一年使用:0次
名校
解题方法
10 . 已知向量
,
,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6c57bbef89a37f1a3808c0ceeac0c22.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a50d86fc2de06e6f7758d1912404c641.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44bd92457a1807a6672738244e6f4153.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6598c54efb953db9d03db4fc330ecb0a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6c57bbef89a37f1a3808c0ceeac0c22.png)
您最近一年使用:0次