题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065749-71397.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065750-85844.gif)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065750-63609.gif)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065750-63706.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065750-44660.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-33189.gif)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-20567.gif)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-81789.gif)
有
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-64096.gif)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-75674.gif)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065752-99423.gif)
又因为
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065752-71814.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065752-24247.gif)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065752-22925.gif)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065753-51252.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065753-77394.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065753-75434.gif)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-33189.gif)
(2)在三角形ABC中,由余弦定理可得
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065753-63520.gif)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065753-60446.gif)
所以有
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065754-69676.gif)
所以所求三角形的面积为
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065751-20567.gif)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065742-78668.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065742-11683.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065742-53392.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065743-86165.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065743-31206.gif)
(2)求C的最大值,并判断此时
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065742-78668.gif)
△ABC中,AB=3,AC=2,BC=
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065738-79828.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065739-46875.gif)
A.-![]() | B.-![]() | C.![]() | D.![]() |
△ABC中,
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065735-16142.gif)
A.30° | B.45° | C.60° | D.90° |
△ABC中,∠C=90°,
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065732-30738.gif)
A.5 | B.-5 | C.![]() | D.-![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065724-15562.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065724-89398.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065724-22167.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065724-90872.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191020/20191020065725-43419.gif)
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