1 . 如图,正方体
的棱长为1,
分别为
的中点,过直线
的平面分别与棱
交于点
.设
,给出以下四个结论:
![](https://img.xkw.com/dksih/QBM/2020/7/10/2503000483315712/2503858342428673/STEM/cd1609fd1e5343b39da958d419aa65d7.png?resizew=198)
①平面
平面
;
②当且仅当
时,四边形
的面积最小;
③四边形
的周长
是单调函数;
④四棱锥
的体积是定值.
其中正确结论的序号为______ (请写出所有正确结论的序号).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad056c25c0fdcbcc765eb5cbc6093f2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8e86e3991200297ad172455e5ea93f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31be3b7305d6c181420ea7b28c420851.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789a500686c7a73770404ead6af0590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d87dccaf9f65ef67b126e9cf94bd8694.png)
![](https://img.xkw.com/dksih/QBM/2020/7/10/2503000483315712/2503858342428673/STEM/cd1609fd1e5343b39da958d419aa65d7.png?resizew=198)
①平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c1f56858867e7b6becaeac49112a3d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2bf9ef324f1289e205e29fed105c38e.png)
②当且仅当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b650820d7bed48ed67a2869ad8c65ff1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65e92eac740953aa383be636ea90fd47.png)
③四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65e92eac740953aa383be636ea90fd47.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20a1d36150a026bbd7a16b8bc936e214.png)
④四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1cb21d0d3f430f009b677eb8945323e1.png)
其中正确结论的序号为
您最近一年使用:0次
解题方法
2 . 已知函数
,给出下列命题:
①
,使
为偶函数;
②若
,则
的图象关于
对称;
③若
,则
在区间
上是增函数;
④若
,则函数
有2个零点.
其中正确命题的序号为_______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1b9b8ebe4891ba96eb7ee9e720668d5.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f05595aa7994885ed05f1de0033da31a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
②若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/90273593dca08da1b9e33e3a8663c514.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b384412acba251d87902ab928902f16.png)
③若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c8e281e0aebdba052969bf11cf86430.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fe7d5809da02c15a43a0e9a898b9086.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92a06dbd1f872110960fe075c079aa67.png)
④若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efd8c7152402dd8cb49b68996655c152.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/50586d67e9c986b57a2a78ab9c187214.png)
其中正确命题的序号为
您最近一年使用:0次