题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065317-21506.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065317-86484.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-83957.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-37009.gif)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-54502.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-34994.gif)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-50554.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-48710.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-14767.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-54502.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-82843.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-65933.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065320-49130.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065320-36066.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-54502.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065320-38274.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065321-71914.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-34994.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065321-85592.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065321-94512.gif)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065319-50554.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065321-35480.gif)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065318-37009.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065321-59278.gif)
讨论:若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065322-28275.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065322-69603.gif)
若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065322-61577.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065323-28046.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065323-97819.gif)
若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065323-34169.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065323-35023.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065324-15483.gif)
综合可得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065323-97819.gif)
解析
核心考点
试题【已知向量,,且(1)求并判断x为何值时;(2)若的最小值是,求的值。】;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/20191104/20191104065307-94884.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065308-29818.png)
①
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065308-66933.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065308-52843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065308-80019.png)
③
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065308-68539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065309-81373.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065309-74628.png)
其中能使
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065309-93780.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065309-38800.png)
A.①② | B.②④ | C.①③ | D.③④ |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065303-98785.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104065304-48278.gif)
A.![]() | B.-5 | C.4 | D.-4 |
A.![]() | B.![]() | C.![]() | D.![]() |
(本题满分12分)
已知|a|=1,|b|=2,
(1)若a∥b,求a·b
(2)若a、b的夹角为60°,求|a+b|;
(3)若a-b与a垂直,求a与b的夹角.
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