解题方法
1 . 已知正方体
的棱长为1,
、
分别为棱
、
的中点,
为棱
上的动点,
为线段
的中点.则下列结论中正确序号为______ .
①
;②
平面
;③
的余弦值的取值范围是
;④△
周长的最小值为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/394c5d2f55221975503be8aa18022480.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11ddc92d84d188c66b435664a7e7b5a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cfbc0b5a8fbde804bd8425a4b76d207.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fe89951021988a68b8eda8d98c5c5570.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0a66d1d242f5317fcc90fee9a8e9fa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/52173c8cc44246823c2bee21a783b731.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/46060ff16376f584eb554e09686ab703.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0814258cf5e34be916ea7774e896738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f06ed3e88f623ed9313d06b1bb2a87ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0487690814e606b108853b9ed32de87.png)
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解题方法
2 . 生态学研究发现:当种群数量较少时,种群近似呈指数增长,而当种群增加到定数量后,增长率就会随种群数量的增加而逐渐减小,为了刻画这种现象,生态学上提出了著名的逻辑斯谛模型:
,其中
,r,K是常数,
表示初始时刻种群数量,r叫做种群的内秉增长率,K是环境容纳量.
可以近似刻画t时刻的种群数量.下面给出四条关于函数
的判断:
①如果
,那么存在
;
②如果
,那么对任意
;
③如果
,那么存在
在t点处的导数
;
④如果
,那么
的导函数
在
上存在最大值.
全部正确判断组成的序号是___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0258e2eee3b3aced0fccf7bf2f5a7e88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de8ece3bf786bbeac646570f1a406e26.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de8ece3bf786bbeac646570f1a406e26.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e108b8fecde4ba66124709e92aeeb2d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e108b8fecde4ba66124709e92aeeb2d.png)
①如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6615283e5cd3420c7876a0db8f810dd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c0ba751b23c41727bf0dc624b0df1674.png)
②如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c66ea216910348bd1e0fbf11bf8a8da4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5d2ce55fe4f1711d88ce831826668641.png)
③如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c66ea216910348bd1e0fbf11bf8a8da4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e3bb3ad142613a6cca7c0aef75e679c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0661d5771343bae8c083037a5267500e.png)
④如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9a25c984f2b12c2a79db640fa308147.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e108b8fecde4ba66124709e92aeeb2d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d87c01dc5d03297b653a48a5ca68de2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1582e9d437ddf096b90257714a250a54.png)
全部正确判断组成的序号是
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