题目
题型:月考题难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092637-13767.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092637-81291.png)
(1)用
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092637-10704.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092638-78041.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092638-58442.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092638-24443.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092638-53659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092639-17875.png)
在△AOB中,|OB|=2,
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092639-46006.png)
由正弦定理,得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092639-81585.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092640-90437.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092640-42542.png)
(2)解:由(Ⅰ)得
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092640-84503.png)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092640-84991.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092641-79979.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092641-53506.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092641-86463.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092641-16296.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092642-74787.png)
核心考点
试题【如图,在平面直角坐标系xOy中,点A在x轴正半轴上,直线AB的倾斜角为,|OB|=2,设.(1)用表示点B的坐标及|OA|;(2)若,求的值.】;主要考察你对平面向量数量积的运算等知识点的理解。[详细]
举一反三
(1)求角B的大小;
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092631-23240.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092631-34596.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092627-75744.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092628-65029.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092611-27516.png)
(Ⅰ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092611-78709.png)
(Ⅱ)设△ABC的三边a,b,c满足b2=ac,且边b所对应的角为x,若关于x的方程
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092611-81518.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092606-93661.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191104/20191104092607-21439.jpg)