题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140717-84728.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140717-70097.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-84126.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-20168.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-94312.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-94833.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140717-84728.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-87885.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-44323.png)
解析
试题分析:(1)本小题的突破口主要是抓住条件
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-20168.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-50647.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-87885.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-18415.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140720-40539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140720-89946.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140720-98214.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140720-35440.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140721-64942.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140718-94833.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-44323.png)
试题解析:(1)由条件结合正弦定理得,
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140721-36486.png)
从而
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-50647.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140721-45718.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140721-74690.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-87885.png)
(2)法一:由正弦定理得:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140721-32363.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-18415.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140720-40539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140722-86510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140722-62722.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140722-85961.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140722-20324.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-11082.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-47624.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-79453.png)
从而
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-15864.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-44323.png)
法二:由已知:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140724-14860.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140724-37661.png)
由余弦定理得:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140724-80787.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140724-44778.png)
(当且仅当
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140724-22390.png)
∴(
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140725-50885.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140725-28904.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-47624.png)
从而
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140723-15864.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140719-44323.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140702-29954.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140646-47064.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-91985.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-85816.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-70737.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-94632.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-55829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140648-97095.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140648-96751.png)
(1)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140648-97095.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140648-45555.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140646-47064.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140648-28824.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140647-70737.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140638-89032.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140620-82724.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140620-31323.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140620-17852.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140620-83565.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140620-10232.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140621-16228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140621-20574.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140547-95015.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140547-78532.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140547-79417.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140548-39158.png)
(1)求角
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140548-85255.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140548-33781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140548-46212.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019140547-95015.png)
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