题目内容
在△ABC中,内角A、B、C的对边分别是
,![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655179682.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655257278.gif)
,
,
(1)求内角A;
(2)求函数
的最小正周期,并写出它的单调增区间。
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655163260.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655179682.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655257278.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655257265.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655288396.gif)
(1)求内角A;
(2)求函数
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655303794.gif)
(1)
(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655319821.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655303230.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655319821.gif)
(1)
,得
,在
中,由余弦定理得,![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655397600.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655413272.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655428580.gif)
,
由正弦定理得,
.
(2)由(1)知,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655303794.gif)
,
函数
的最小正周期为T=2π,由
,
,故y=f(x)的单调增区间为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/2014082314265586573.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655319821.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655335418.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655350639.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655366400.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655397600.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655413272.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655428580.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655444545.gif)
由正弦定理得,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655569995.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655584304.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655600491.gif)
(2)由(1)知,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655303794.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655631971.gif)
函数
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655834421.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655849752.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655865716.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/2014082314265586573.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823142655319821.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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