题目
题型:不详难度:来源:
在
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-29929.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-53622.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-73480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-97978.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-97978.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-97978.png)
⑴求
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123813-76145.png)
⑵判断
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123813-61238.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123813-41869.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123814-71429.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123814-21560.png)
解析
(1)第一问利用平面向量基本定理表示出
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123814-69377.png)
(2)利用设出平面坐标系来表示点,然后借助于向量的数量积得到结论。
解法1:(1)因为
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-14258.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123812-73480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-61582.png)
由已知可得
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-14573.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-71811.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-91501.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123816-79546.png)
=
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123816-33526.png)
(2
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123816-88516.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123813-61238.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123817-15771.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123815-91501.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123817-52062.png)
故
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123817-26784.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123818-98258.png)
解法2:(1)以D点为原点,BC所在直线为X轴,L所在直线为Y轴建立直角坐标系,可求A(
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123818-87609.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123818-37802.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123818-53298.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123819-45072.png)
(2)设E点坐标为(0,y)(y
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123819-77542.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123819-83748.png)
此时
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123819-84734.png)
核心考点
试题【(本题满分9分)在中,,为线段BC的垂直平分线,与BC交与点D,E为上异于D的任意一点,⑴求的值。⑵判断的值是否为一个常数,并说明理由。】;主要考察你对空间向量的线性运算等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123806-98289.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123807-63066.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123807-47277.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123807-38593.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123807-54704.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123808-63225.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123808-35113.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123808-18845.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123800-14350.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123800-27947.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-29910.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-81846.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-23109.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-85894.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-66712.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123801-11096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123802-96145.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123753-29470.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123753-71246.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123753-45564.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123753-29470.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123746-43169.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123747-74938.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123746-43169.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123747-74938.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123747-25849.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123747-33395.png)
(2)|
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105123747-41263.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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