题目内容
已知函数
,其中常数
;
(1)若
在
上单调递增,求
的取值范围;
(2)令
,将函数
的图像向左平移
个单位,再向上平移1个单位,得到函数
的图像,区间
(
且
)满足:
在
上至少含有30个零点,在所有满足上述条件的
中,求
的最小值.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747353804.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747369418.png)
(1)若
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747384562.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747400651.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747415308.png)
(2)令
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747415419.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747384562.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747447420.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747462548.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747478433.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747493534.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747493412.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747462548.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747478433.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747478433.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747556387.png)
(1)
(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747587531.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747571619.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747587531.png)
(1)因为
,根据题意有
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240157476031539.png)
(2)
,![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240157476341473.png)
或
,
即
的零点相离间隔依次为
和
,
故若
在
上至少含有30个零点,则
的最小值为
.
【考点定位】考查三角函数的图象与性质,三角函数图象的平移变换,属中档题
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747369418.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240157476031539.png)
(2)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747618747.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240157476341473.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240157476491508.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747649882.png)
即
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747681442.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747696413.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747712491.png)
故若
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747462548.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747478433.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747556387.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824015747759980.png)
【考点定位】考查三角函数的图象与性质,三角函数图象的平移变换,属中档题
![](http://thumb.zyjl.cn/images/loading.gif)
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