题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-66739.png)
(1)求函数f(x)在[0,π]上的单调递减区间;(2)△ABC中,
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-76316.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-62331.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-11045.png)
解析
试题分析:(1)根据辅助角公式,函数的最大值为
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-18533.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-15238.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-67492.png)
试题解析:(1)由题意,f(x)的最大值为
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-18533.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-76993.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-66739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115804-78848.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115804-62017.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115804-66216.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-62331.png)
(2)设△ABC的外接圆半径为R,由题意,得
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115804-63903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115802-76316.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115804-30886.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115805-95650.png)
将①式代入②,得2(ab)2-3ab-9=0,解得ab=3或
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115805-81918.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115805-92480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115803-67492.png)
核心考点
试题【已知函数f(x)=msinx+cosx(m>0)的最大值为2. (1)求函数f(x)在[0,π]上的单调递减区间;(2)△ABC中,角A,B,C所对的边分】;主要考察你对正弦定理等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115733-61287.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115720-52312.png)
(1)求角A的大小; (2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019115720-52313.png)
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