如图,四面体ABCD中,O、E分别是BD、BC的中点,CA=CB=CD=BD=2,AB=AD=
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(I)求证:AO⊥平面BCD;
(II)求异面直线AB与CD所成角的大小;
(III)求点E到平面ACD的距离.
考点分析:
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已知函数f(x)=2sinωxcosωx-2cos
2ωx(x∈R,ω>0),相邻两条对称轴之间的距离等于
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.
(Ⅰ)求
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的值;
(Ⅱ)当
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时,求函数f(x)的最大值和最小值及相应的x值.
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将函数
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的图象向右平移a(a>0)个单位,所得图象的函数为偶函数,则a的最小值为 ( )
A.
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B.
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C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183557596392586/SYS201310241835575963925019_ST/3.png)
D.
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[理科]观察下列式子:
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183557596392586/SYS201310241835575963925018_ST/0.png)
,
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,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183557596392586/SYS201310241835575963925018_ST/2.png)
,…,可以猜想结论为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131024183557596392586/SYS201310241835575963925018_ST/3.png)
B.
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C.
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D.
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关于x、y的二元一次方程组
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的系数行列式D=0是该方程组有解的( )
A.充分非必要条件
B.必要非充分条件
C.充分且必要条件
D.既非充分也非必要条件
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已知α,β为不重合的两个平面,直线m⊂α,那么“m⊥β”是“α⊥β”的( )
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B.必要而不充分条件
C.充分必要条件
D.既不充分也不必要条件
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