题目
题型:不详难度:来源:
在平面直角坐标系
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075118-77964.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075119-86130.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075119-50529.gif)
(1)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075119-60022.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075119-94291.gif)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075120-48981.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075120-92970.gif)
答案
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075120-66827.gif)
解析
由题设知
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075120-78675.gif)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075121-96343.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075121-78430.gif)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075121-94931.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075121-38958.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-27307.gif)
(方法二)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075121-94931.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-54802.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-71599.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-84321.gif)
因此
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075123-55434.gif)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075123-14468.gif)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-27307.gif)
(2)因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075123-98745.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075124-78882.gif)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075124-61765.gif)
解得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075124-33744.gif)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075122-54802.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075124-25760.gif)
因此
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075125-59803.gif)
从而
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075125-18982.gif)
核心考点
试题【(本小题满分14分)在平面直角坐标系中,已知点其中.(1)若求证:(2)若求的值.】;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/20191104/20191104075113-19808.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075113-82205.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075107-95171.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075107-97575.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075102-55550.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075102-32705.gif)
A.![]() | B.2 | C.-2 | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075051-92947.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075053-56636.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075053-13124.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075053-28847.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075053-92368.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075053-64909.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075046-91328.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075046-82070.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075046-95059.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104075047-17794.gif)
A.-7 | B.9 | C.4 | D.-4 |
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