题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-46260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-58153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-40916.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-41408.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-32979.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-66147.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-46260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-58153.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-35450.png)
解析
【错解分析】由题意,得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-39693.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-42766.png)
将①、②展开并相减,得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-80998.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-61450.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-45967.png)
将④代入②,得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-23822.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-56449.png)
设
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-46260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-58153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-98019.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054404-74666.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054404-71337.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-35450.png)
【正解】设向量
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-46260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054400-58153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-98019.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-39693.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-42766.png)
将①、②展开并相减,得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-80998.png)
有
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054404-62943.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-23822.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054403-56449.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054404-83032.png)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054405-69107.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054401-35450.png)
【点评】错解中解法表面上是正确的,但却存在着一个理解上的错误,即由③得到④,错把数的乘法的消去律运用在向量的数量积运算上.由于向量的数量积不满足消去律,所以即使
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054402-61450.png)
核心考点
试题【向量、都是非零向量,且向量与垂直,与垂直,求与的夹角.】;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/20191104/20191104054354-27400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054343-17153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054343-11779.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054343-69599.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054343-16422.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054323-80462.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054323-23632.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054324-37507.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054324-98033.png)
A.![]() | B.![]() | C.4 | D.2 |
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-62002.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-32766.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-98176.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054312-13032.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-98176.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-32766.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054312-31596.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-32766.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104054311-98176.png)
A.![]() | B.![]() | C.![]() | D.![]() ![]() |
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