题目内容
(12分)如图所示,正方形
和矩形
所在平面相互垂直,
是
的中点.
(I)求证:
;
(Ⅱ)若直线
与平面
成45o角,
求异面直线
与
所成角的余弦值.![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231632318795313.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231302213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231318232.gif)
(I)求证:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231489432.gif)
(Ⅱ)若直线
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231505236.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
求异面直线
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231552241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231677238.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231632318795313.jpg)
(1) 略
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231895268.gif)
(I)证明:在矩形
中,
∵ 平面![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
平面
,且平面![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
平面![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232254253.gif)
∴
∴
--------------6分
(Ⅱ)由(I)知:![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232285606.gif)
∴
是直线
与平面
所成的角,即![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232332294.gif)
-----------8分
设![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232503705.gif)
取
,连接![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232535362.gif)
∵
是
的中点 ∴![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232597461.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/2014082316323269116171.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231957331.gif)
∵ 平面
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232160108.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231287412.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232223152.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232254253.gif)
∴
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232285606.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231489432.gif)
(Ⅱ)由(I)知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232285606.gif)
∴
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232332294.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231505236.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231271303.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232332294.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232488241.gif)
设
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232503705.gif)
取
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232519488.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232535362.gif)
∵
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231302213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163231318232.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823163232597461.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/2014082316323269116171.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目