题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075009-66329.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-89943.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-52991.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-42796.gif)
(Ⅰ)若对任意实数t都有
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075011-54007.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-52991.gif)
(Ⅱ)令
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075011-53244.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075011-74213.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-52991.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075012-93758.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075012-61462.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075011-74213.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-52991.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075012-38797.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075011-74213.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075010-52991.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075012-42850.gif)
(Ⅲ)在(Ⅱ)的条件下,求
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-94372.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-40816.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-70052.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-38562.gif)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075014-97565.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075014-19990.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075014-82330.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075015-68142.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-40816.gif)
(Ⅱ)易知
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075015-39381.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075015-16370.gif)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075015-74540.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075016-24764.gif)
∴3sin22α+sin2αcos2α-2cos4α)="0 " ……………………(7分)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075016-91975.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075016-91975.gif)
∵α∈(
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075012-38797.gif)
故2sinα+cosα="0 " ……………(9分)
∴tanα=-
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-70052.gif)
(Ⅲ)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-94372.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075016-70843.gif)
=
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075016-92487.gif)
=
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075017-48290.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075017-88778.gif)
=
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075017-34199.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075013-38562.gif)
核心考点
试题【(本小题满分14分)已知平面向量=(,-1),=(x,y)(x>0),=1.(Ⅰ)若对任意实数t都有,求向量;(Ⅱ)令=+(sin2α-2cos2α),=】;主要考察你对平面向量数量积的意义等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075005-33351.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075005-66291.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075006-74556.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075006-86454.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075006-94868.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075001-81066.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075001-43633.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075001-56861.gif)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075003-31125.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074957-16618.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
已知向量
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074949-80000.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074949-89694.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074949-94261.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074949-42998.gif)
(Ⅰ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074950-24658.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074950-27758.gif)
(Ⅱ)当
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074950-59256.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074950-86633.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074951-44967.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074951-22233.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074945-47556.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074945-99692.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104074945-77880.gif)
A.![]() | B.![]() | C.![]() | D.4 |
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