题目内容
已知函数f(x)=2sin
(0≤x≤5),点A、B分别是函数y=f(x)图象上的最高点和最低点.
(1)求点A、B的坐标以及
·
的值;
(2)设点A、B分别在角α、β的终边上,求tan(α-2β)的值.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023078857.png)
(1)求点A、B的坐标以及
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023109394.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023109382.png)
(2)设点A、B分别在角α、β的终边上,求tan(α-2β)的值.
(1)3(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023125446.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023125446.png)
(1)∵0≤x≤5,∴
≤
≤
,
∴-
≤sin
≤1.
当
=
,即x=1时,sin
=1,f(x)取得最大值2;
当
=
,即x=5时,sin
=-
,f(x)取得最小值-1.
因此,点A、B的坐标分别是A(1,2)、B(5,-1).
∴
·
=1×5+2×(-1)=3.
(2)∵点A(1,2)、B(5,-1)分别在角α、β的终边上,
∴tan α=2,tan β=-
,
∵tan 2β=
=-
,∴tan(α-2β)=
.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023140413.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023156635.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023172491.png)
∴-
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023187338.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023078857.png)
当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023156635.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023250421.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023078857.png)
当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023156635.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023172491.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023078857.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023187338.png)
因此,点A、B的坐标分别是A(1,2)、B(5,-1).
∴
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023109394.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023109382.png)
(2)∵点A(1,2)、B(5,-1)分别在角α、β的终边上,
∴tan α=2,tan β=-
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023390308.png)
∵tan 2β=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023406826.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824040023421409.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240400234211055.png)
![](http://thumb.zyjl.cn/images/loading.gif)
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