题目内容
已知向量
,
满足|
|=3|
|≠0,且关于x的函数f(x)=
x3+
|
|x2+
·
x在R上单调递增,则
,
的夹角的取值范围是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852824321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852824321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853042343.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853042343.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852824321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852824321.png)
A.[0, ![]() | B.[0, ![]() | C.(![]() ![]() | D.(![]() ![]() |
B
本题主要考查的是导数与向量的综合。由条件可知,
。要使函数f(x)在R上单调递增,应满足
恒成立,即
,
。又|
|=3|
|≠0,代入整理得
,所以应选B。
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231918533541033.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853370959.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853385697.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853417973.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852793300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191852824321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823191853463624.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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