题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031545-78819.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031545-60322.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031545-34227.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031545-16932.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031546-75181.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031546-95292.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031546-70712.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031546-74366.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-59184.png)
(1)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031545-78819.png)
(2)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-40763.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-55037.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-15804.png)
解析
试题分析:(1)利用
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-92935.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031548-86825.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-55037.png)
(2)利用和差化积化简cosA+cosC=2cos
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031548-86381.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031548-23258.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031548-28732.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031548-62086.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-63512.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-63512.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-63512.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-55037.png)
试题解析:(1)∵
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-72664.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-59550.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-70204.png)
由正弦定理得
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031550-44696.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031550-65961.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031550-15176.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031550-10479.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031550-80809.png)
9分
由(1)知A∈(0,
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031549-63512.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031551-30942.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031551-72625.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-40763.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031547-15804.png)
核心考点
举一反三
A.一定是锐角三角形 |
B.一定是直角三角形 |
C.一定是钝角三角形 |
D.可能是锐角三角形,也可能是钝角三角形 |
A.![]() | B.![]() | C.-![]() | D.-![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031527-99695.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031527-50249.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031527-99695.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031527-99695.png)
(1)求函数f(A)的最大值;
(2)若f(A)=0,C=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031528-62931.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031528-37404.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031519-93126.png)
(1)求cos(A+C)的值;
(2)求sin
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031519-96735.png)
(3)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031520-46948.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020031520-16048.png)
A.30°或60° | B.45°或60° |
C.120°或60° | D.30°或150° |
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