名校
1 . 下列命题正确的个数为( )
①长方体
中,
,
,则异面直线
与
所成角的余弦值为
;
②对于命题:
,
,则命题
的否定:
,
;
③ “
”是“
”的充分不必要条件;
④已知
,
,
,且
,则
的值为
.
①长方体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/829018a6ca0aff95d89e3f7cd943274e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92535536bd3c2761724fd058427f95a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83c09eec4e14a861af83d7828797d176.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e64e76a4c1e5934f51cdca2ffbc8313f.png)
②对于命题:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/02491f9709f00a1bc169278fbe01f576.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecd0737f120bf1bae03b9abbae79e4ec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d96b743603ab1c10330622f16db78dbe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/654120ab17a29dbae5cf9c43860846ca.png)
③ “
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ae8adaa3d42ccb9d59e0d6b6f60bf73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5553e7018e6e14755bbcda2b657c7b03.png)
④已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/26b566395b41fc587143d533f9756024.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22fc7939259f787ce6d557e59bb3dc15.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1b1ba2e2dbab8c7bec0dad6b63fcc5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da1e517c0d481c5d62707ed3f6435d71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dac452fbb5ef6dd653e7fbbef639484.png)
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