证明:(1)![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-38767.gif) ∥ -------------------------------------2分
又 面 -----------------------------------------------------1分
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015011-41788.gif) 面 ------------------------------------------------------1分
∥面 ------------------------------- -----------------------1分 (2)![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-38767.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-35071.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-74301.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015013-76155.gif) 又![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-38767.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-35071.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-74301.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015013-33781.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-62581.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-35071.gif) 面![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-31288.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-38767.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-34213.gif) 面![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-31288.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-62581.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-34213.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-74301.gif) ----------------------------------2分 连接 ,同理可证![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-64496.gif) 面 ---------------2分
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-38767.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-34213.gif) 面![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015015-50498.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-62581.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-34213.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015012-74301.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-64496.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-62581.gif) ![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021015014-34213.gif) 面 ----------------------------------------------1分 |