题目内容
(.(9分)如图所示三棱锥P—ABC中,异面直线PA与BC所成的角为
,二面角P—BC—A为
,△PBC和△ABC的面积分别为16和10,BC=4. 求:
(1)PA的长;(2)三棱锥P—ABC的体积![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728883386.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728696247.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728711248.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728883672.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728883386.gif)
PA=7;(2)V=![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728914337.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728914337.gif)
(1)作AD⊥BC于D,连PD,由已知PA⊥BC,∴BC⊥面PAD,∴BC⊥PD,∴∠PDA为二面角的平面角,∴∠PDF=
,可算出PD=8,AD=5,∴PA=7;(2)V=![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728914337.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728711248.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823143728914337.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目
题目内容