如图,在三棱锥
中,
平面ABC,点D,E,F分别为PC,AB,AC的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/6/f1c930c8-c484-49cb-aa40-23ab41bc30a0.png?resizew=182)
(Ⅰ)求证:
平面DEF;
(Ⅱ)求证:
.
阅读下面给出的解答过程及思路分析.
解答:(Ⅰ)证明:在
中,因为E,F分别为AB,AC的中点,所以①.
因为
平面DEF,
平面DEF,所以
平面DEF.
(Ⅱ)证明:因为
平面ABC,
平面ABC,所以②.
因为D,F分别为PC,AC的中点,所以
.所以
.
思路分析:第(Ⅰ)问是先证③,再证“线面平行”;
第(Ⅱ)问是先证④,再证⑤,最后证“线线垂直”.
以上证明过程及思路分析中,设置了①~⑤五个空格,如下的表格中为每个空格给出了三个选项,其中只有一个正确,请选出你认为正确的选项,并填写在答题卡的指定位置.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/6/f1c930c8-c484-49cb-aa40-23ab41bc30a0.png?resizew=182)
(Ⅰ)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/963a91995abd4927d75406d16e10a81f.png)
(Ⅱ)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d276d0010fd458383ea3dd61415e1aa.png)
阅读下面给出的解答过程及思路分析.
解答:(Ⅰ)证明:在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
因为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4fa6d320a49764f0fbd3df95bde452a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70b102c0fb7a1e3911e22535579ffa84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/963a91995abd4927d75406d16e10a81f.png)
(Ⅱ)证明:因为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8690d88536618e3f993dae41a3de66a.png)
因为D,F分别为PC,AC的中点,所以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cb5dc3315629bf14991d5c4feb3a1ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d276d0010fd458383ea3dd61415e1aa.png)
思路分析:第(Ⅰ)问是先证③,再证“线面平行”;
第(Ⅱ)问是先证④,再证⑤,最后证“线线垂直”.
以上证明过程及思路分析中,设置了①~⑤五个空格,如下的表格中为每个空格给出了三个选项,其中只有一个正确,请选出你认为正确的选项,并填写在答题卡的指定位置.
空格 | 选项 | ||
① | A.![]() | B.![]() | C.![]() |
② | A.![]() | B.![]() | C.![]() |
③ | A.线线垂直 | B.线面垂直 | C.线线平行 |
④ | A.线线垂直 | B.线面垂直 | C.线线平行 |
⑤ | A.线面平行 | B.线线平行 | C.线面垂直 |
更新时间:2019-10-22 16:55:58
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名校
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