1 . 如图所示的八面体的表面是由2个全等的等边三角形和6个全等的等腰梯形组成,设
,
,有以下四个结论:
①
平面
; ②
平面
;
③直线
与
成角的余弦值为
④直线
与平面
所成角的正弦值为
.
其中正确结论的个数是( )
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/28/34f390e6-ecea-44bc-8ad5-62f5deb3aaf8.png?resizew=195)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab1bdb08d371f24f7b4aeae53f292050.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2ffc6952e988d04f22f0fb2f7f0ab7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c50346190b81576e0d891456af44490.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/780d4680b5fd79c9734c4439e28cdf3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7312cd653ef43a6ab81dd5da81cac779.png)
③直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04c8b7a498f2fa0820ad123a8756ce64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c6c7567972273b4ba733b47bf9d5408.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f1f229274a6e17977cc047814212589.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fd6a02542c1ee2d2a60ea0a9ce7e82d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1174142f3bba761585b6bc2653009b36.png)
其中正确结论的个数是( )
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/28/34f390e6-ecea-44bc-8ad5-62f5deb3aaf8.png?resizew=195)
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