题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045141-87895.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045141-37969.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-27294.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
根据面积公式得S△ABC="1" /2 AB•BCsinB
="1/" 2 ×2x
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-23431.png)
根据余弦定理得cosB=(AB2+BC2-AC2)/2AB•BC=[4+x2-(
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
代入上式得
S△ABC=x
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-99481.png)
由三角形三边关系有
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
x+2>
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
解得2
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
故当x=2
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045143-27978.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045142-45243.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045134-46542.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-47217.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-80445.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-19260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-17651.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-70879.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-43888.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-44153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-74897.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-43888.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045134-46542.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-88240.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-71665.jpg)
(1) 将
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-82725.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-44678.png)
(2)已知常数
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-47024.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-62151.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-41435.png)
且仅当
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-36153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-43888.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045136-77561.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045135-88240.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045126-95202.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045127-78798.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045127-41628.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045127-77525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045127-10657.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045127-61469.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045128-24997.png)
A.2 | B.![]() | C.![]() | D.1 |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045121-56551.png)
A.有两个解 | B.有一个解 | C.无解 | D.有无数个解 |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045117-77329.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020045118-55164.png)
A.120° | B.60° | C.60或120° | D.45° |
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