题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043221-47016.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043221-22038.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043221-90397.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043221-15400.png)
(Ⅰ)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-57005.png)
(Ⅱ)设函数
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-93360.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-13442.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043221-47016.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-72228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-13442.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-16722.png)
解析
试题分析:(Ⅰ)在△ABC中,因为b2+c2-a2=bc,由余弦定理 a2= b2+c2-2bccosA 可得cosA=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043223-46261.png)
∵ 0<A<π , (或写成A是三角形内角) ∴
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-72228.png)
(Ⅱ)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-93360.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043223-43754.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043223-21550.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-72228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043223-61575.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043223-69076.png)
∴当
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043224-21233.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043224-11031.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-13442.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-16722.png)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043222-72228.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043224-96475.png)
点评:解三角形时应用正余弦定理实现边角的互相转化,三角函数性质的考查要结合图像分析求解
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043213-95112.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043213-15039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043214-93412.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043214-55834.png)
(Ⅰ)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043214-69130.png)
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043214-89959.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043214-29008.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043213-95112.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043204-27957.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043205-71382.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043205-44141.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043205-45037.png)
(Ⅰ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043205-69559.png)
(Ⅱ)设
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043205-90119.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043206-28255.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043206-33684.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043206-64009.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043206-49659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043207-46069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-75852.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-29289.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-54140.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-10366.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-46731.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043158-11376.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043158-37867.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043157-75852.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043149-13307.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043149-42835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043150-55104.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043150-76914.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043150-62835.png)
(Ⅰ)求角A的大小;
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043150-46730.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043149-13307.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-85433.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-60721.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-64090.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-96547.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-73174.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043142-59294.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043142-37200.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043142-52555.png)
(1)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043141-96547.png)
(2)设函数
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043142-57809.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043143-88122.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043143-63081.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020043143-39611.png)
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