题目内容
(8分)如图,四棱锥
底面是正方形且四个顶点
在球
的同一个大圆(球面被过球心的平面截得的圆叫做大圆)上,点
在球面
上且
面
,且已知
。
(1)求球
的体积;
(2)设
为
中点,求异面直线
与
所成角的余弦值。![](http://thumb.1010pic.com/pic2/upload/papers/20140823/2014082316040955872.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231604095737384.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409168347.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409183334.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409199209.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409214202.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/2014082316040923072.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409246262.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409277234.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409339537.gif)
(1)求球
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409199209.gif)
(2)设
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409370327.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409495241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409511364.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409526236.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/2014082316040955872.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231604095737384.jpg)
(1)球
的体积![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409620495.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409776414.gif)
(2)
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409199209.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409620495.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409776414.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409792691.gif)
解:(1)设球
的半径为
,则![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409870404.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409885218.gif)
所以
,![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409948652.gif)
,所以
,——3
所以球
的体积![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409620495.gif)
(2)取
的中点
,连结
,则![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410790455.gif)
所以
为异面直线
与
所成角。
由已知
,
,![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410915697.gif)
所以
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409199209.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409838204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409870404.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409885218.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409901440.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409916476.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409948652.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409963275.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410322248.gif)
所以球
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409199209.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409620495.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409776414.gif)
(2)取
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410494234.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410509211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410572452.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410790455.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410821431.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409511364.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409526236.gif)
由已知
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410884929.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410899843.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160410915697.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823160409792691.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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