题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-53638.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-95196.png)
(1)求角C;
(2)求a、
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-18843.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-67612.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-18843.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-53638.png)
因为(
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-70197.png)
从而借助
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-46472.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-56885.png)
(2)由S=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-41917.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-34371.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-95196.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-87568.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-88459.png)
从而可求a+b,然后再与ab=40解方程组可求出a,b的值.
(1)设
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-53638.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-93884.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-68082.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044656-66476.png)
∴(
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-46162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-60414.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044656-94413.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044656-87650.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-70197.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-46472.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-41917.png)
(2)由S=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044654-41917.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-34371.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044652-95196.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044655-87568.png)
由余弦定理:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044656-53148.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044656-67018.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044657-24756.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044657-93372.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-67612.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044653-18843.png)
核心考点
试题【a,b,c是△ABC的三边长,关于x的方程 (a>c>b)的两根之差的平方等于4,△ABC的面积S=10,c=7.(1)求角C;(2)求a、的值. 】;主要考察你对解三角形应用等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044645-59179.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044645-62533.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044646-80856.png)
(2) △ABC是锐角三角形,函数
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044646-17650.png)
证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044646-60853.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044646-35953.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-23757.png)
现由供水站
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-57110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-58443.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-50575.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-62707.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-77072.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044640-12004.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044640-91548.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044640-26880.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044640-44659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-77072.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044639-77072.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044631-58972.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044631-14311.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044631-92847.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044631-51470.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044632-71197.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044632-92839.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044632-47076.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044632-59737.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044633-66846.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044633-90179.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044633-76660.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044631-92847.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044627-37244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044628-86729.png)
(1)求角C;
(2)求边a。
设
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044621-50132.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044621-91846.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044622-30528.png)
(Ⅰ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044621-50132.png)
(Ⅱ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020044622-52967.png)
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