题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043824-91580.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043824-46921.png)
解析
试题分析:由题意可知A=120°,AB=5,BC=7,那么根据余弦定理,
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043825-93656.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043825-11890.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043825-56589.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043825-22690.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043825-60236.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043824-46921.png)
点评:解决该试题的关键根据已知的两边及其一边的对角,那么能选择合适的定理余弦定理得到b的值,进而利用正弦定理得到求解。
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043812-77440.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-92583.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-35901.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-11714.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-57455.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-40473.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-57548.png)
(1)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-11714.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-49616.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-57455.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-40473.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-57548.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043812-77440.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-92583.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-54275.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043814-98674.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043813-11714.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043805-87881.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-32786.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-41987.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-32786.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-93467.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043805-87881.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043805-87881.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-98625.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-32786.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-64552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043805-87881.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-64552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043807-42518.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043806-32786.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043807-43829.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043801-18718.png)
A.3 | B.![]() | C.![]() | D.2![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043753-82423.png)
(Ⅰ)求函数
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043753-24253.png)
(Ⅱ)设A,B,C为
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043753-16467.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043754-93680.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043754-48944.png)
在△ABC中,内角A、B、C所对边的长分别为a、b、c,已知向量
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043748-12454.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043748-11014.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043748-12454.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043748-11014.png)
(Ⅰ)求A的大小;
(Ⅱ)若a=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043748-42501.png)
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