题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041356-57074.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041356-98186.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041356-20795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041357-74949.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041357-71730.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041357-60882.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041357-27026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041357-64870.png)
(1)求A的大小;
(2)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-40475.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-24359.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-40475.png)
解析
试题分析:(1)由已知,根据正弦定理得
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-78144.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-83737.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-29292.png)
故
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041359-14963.png)
(2)由(1)得:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041359-57294.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041359-44037.png)
故当
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041359-58948.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041358-40475.png)
点评:本题主要考查余弦定理,两角和差的正弦、余弦公式的应用,根据三角函数的值求角,属于中档题.
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041347-59070.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041348-86157.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041348-10424.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041348-80140.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041348-10990.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041348-57276.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041349-68630.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041349-88729.png)
(Ⅰ)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041349-88729.png)
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041349-56604.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041349-88689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041347-59070.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041340-84554.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041341-86391.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041340-84554.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041341-67747.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041341-19901.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041341-69478.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041342-83186.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041340-84554.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041341-86391.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041342-63781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041342-95296.jpg)
如图所示,港口
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041333-29957.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041334-66220.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041334-64295.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041334-26427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041334-98184.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041335-66814.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041334-26427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041335-83340.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041335-78366.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041335-15933.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041335-38912.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041333-29957.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041336-13046.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041330-92454.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041330-90389.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041330-13181.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041322-46768.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041322-37132.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041322-98526.png)
已知向量
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041323-10916.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041323-26793.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041323-49302.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041323-58216.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041324-48294.png)
(1) 求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041324-42001.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041324-78484.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041324-26393.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020041325-13609.png)
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