题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142642-74111.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142642-88701.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142643-66943.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142643-80692.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142643-82369.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142643-94741.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-13478.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-59641.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-65029.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142642-74111.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-26987.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142645-84077.png)
解析
试题分析:(1)由
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142645-29935.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-13478.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142644-13478.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142645-26982.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142645-31424.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142645-14683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-45427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-39338.png)
试题解析:解:(1)法一:由题意知m·n
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-30174.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-21188.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-16078.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-66120.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-55003.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-25563.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-30176.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-43348.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142648-50068.png)
法二:由题意知m·n
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142646-30174.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142648-74478.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142648-43715.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142648-28712.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142649-44090.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142649-54737.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142647-25563.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142648-50068.png)
(2)法一:由余弦定理知
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142649-92823.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142649-32792.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142650-21681.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142650-73516.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142650-15161.png)
∴△
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142642-74111.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142650-16423.png)
法二:由正弦定理可知
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142651-76994.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142651-64802.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142651-71452.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142651-93982.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142651-48880.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142642-74111.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142652-91388.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142351-44717.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142352-20833.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142352-80514.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142352-99207.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142352-29519.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142338-81388.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142338-39613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142338-62172.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142339-78509.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142339-89246.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142339-96704.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142339-46903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142340-41844.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142340-92182.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142324-96544.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142324-18142.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142325-79215.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142324-18142.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142325-18186.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142325-15279.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142305-85237.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142305-10316.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142305-28338.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142305-11967.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142305-85237.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142036-35212.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142036-64660.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-38374.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-11157.png)
(Ⅰ).若
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-74751.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-38374.png)
(Ⅱ).设
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-16199.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-54713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019142037-38374.png)
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