下列四个命题中,其中真命题是( )
①“若xy=1,则lgx+lgy=0”的逆命题;
②“若
•
•
,则
⊥(
)”的否命题;
③“若b≤0,则方程x2﹣2bx+b2+b=0有实根”的逆否命题;
④“等边三角形的三个内角均为60°”的逆命题.
①“若xy=1,则lgx+lgy=0”的逆命题;
②“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2859333183a1d5749eac25f8b4e3b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1098e4b4dd1553c6bd70b83b85a99a9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/847fb7661543522ad8935b9057a18b6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2859333183a1d5749eac25f8b4e3b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a0f25f59d7373676d944abce18c8bf7.png)
③“若b≤0,则方程x2﹣2bx+b2+b=0有实根”的逆否命题;
④“等边三角形的三个内角均为60°”的逆命题.
A.①② | B.①②③④ | C.②③④ | D.①③④ |
2019高三·全国·专题练习 查看更多[1]
(已下线)专题1.2 命题及其关系、逻辑联结词、充分条件与必要条件-《2020年高考一轮复习讲练测》(浙江版)
更新时间:2019-09-04 15:11:49
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【推荐1】给出下列四个命题:①命题“若
,则
”的逆否命题为假命题:
②命题“若
.则
”的否命题是“若
,则
”;
③若“
”为真命题,“
”为假命题,则
为真命题,
为假命题;
④函数![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fdf9e60ecc57b112e3a7c1dfafb85a94.png)
有极值的充要条件是
或
.
其中正确的个数有
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4120436d6ff0c58109473edc068257c3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ffb8898d840443e228d34d94056f081e.png)
②命题“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/432d77fe5ad3032d59a237dd94c8a638.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b68054ddc67a9f7aa81a0343034d3bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3798d6c2e5eac9c1d8b044efd5081acf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/913bb73461c34038362fc5a6a58f39a5.png)
③若“
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f675824e539f50cec53120959d32e554.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c13472bf0353e16784a22e1f890fba40.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
④函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fdf9e60ecc57b112e3a7c1dfafb85a94.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc7858a71a159fe49ef5c817c050e4df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fa204d6b5183969f6da37f369eb7293d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17bda892497cea43df67db57b4e2a07a.png)
其中正确的个数有
A.![]() | B.![]() | C.![]() | D.![]() |
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【推荐2】有下列几个命题:①“若p,则q”的否命题是“若
,则
”;②p是q的必要条件,r是q的充分不必要条件,则p是r的必要不充分条件;③若“
”为真命题,则命题p,q中至多有一个为真命题;④过点
的直线和圆
相切的充要条件是直线斜率为
.其中为真命题的有( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ffc1bb9d53a27d484396ad74d6a26e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e26b38e357c7d985656ba7bb3c794a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11e82b0235513a5f51e150dc420e8fae.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25f114df5ceabdb7e5fd3fdad4eaf056.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f240cccaf24af8a796abb95cb42be52e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b2a698891d42c70b597f0da4f215f09.png)
A.①② | B.①②③ | C.①③④ | D.①②③④ |
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【推荐1】有下列四个命题:
①命题“若
,则
互为倒数”的逆命题;
②命题“面积相等的三角形全等”的否命题;
③命题“若向量
与
的夹角为锐角,则
”的逆命题;
④命题“若
,则
”的逆否命题.
其中真命题的个数是( )
①命题“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/377a2333ff8c63cbdb20b882d6d5a7ec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
②命题“面积相等的三角形全等”的否命题;
③命题“若向量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a92e6eba8dab638fd66831cd3a0b6d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/427fa45527d0ce469bfd060bf6f991f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/059e90867a80383e6e70a8a3de574c67.png)
④命题“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b05d2be27e8f53e4de3071846dffb41.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/caf22d7d1a965bda25168a233fb6290c.png)
其中真命题的个数是( )
A.1 | B.2 | C.3 | D.4 |
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【推荐2】已知
都是实数,则在命题“若
,则
”与它的逆命题、否命题、逆否命题四个命题中,真命题的个数是
![](https://img.xkw.com/dksih/QBM/2016/9/26/1826275741057024/1826275741769728/STEM/642e5ece9ddd4a97b412b6756c751ac3.png)
![](https://img.xkw.com/dksih/QBM/2016/9/26/1826275741057024/1826275741769728/STEM/d1bf585fb1fd42cb913b7e6770895d01.png)
![](https://img.xkw.com/dksih/QBM/2016/9/26/1826275741057024/1826275741769728/STEM/ec184d50a42b4cd0a6472de47f397744.png)
A.4 | B.2 | C.1 | D.0 |
您最近一年使用:0次