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解题方法
1 . 正四面体是侧棱与底面边长都相等的正三棱锥,它的对棱互相垂直.有一个如图所示的正四面体
,E,F,G分别是棱AB,BC,CD的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/e67292c5-8e55-4068-bf10-e6e79ce60ad7.png?resizew=182)
(1)求证:
面EFG;
(2)求异面直线EG与AC所成角的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/891579e7c231584a8e16b8eeff79888e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/e67292c5-8e55-4068-bf10-e6e79ce60ad7.png?resizew=182)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f81fa367ec317fe2a30142e1c30cce7.png)
(2)求异面直线EG与AC所成角的大小.
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