题干

给出下列五个命题:
①函数 y=2sin(2x
π
3
)
的一条对称轴是x= 12
5
π
②函数y=tanx的图象关于点(
π
2
,0)对称;
③正弦函数在第一象限为增函数;
④若 sin(2x1
π
4
)
=sin(2x2
π
4
)
,则x1﹣x2=kπ,其中k∈Z;
⑤函数f(x)=sinx+2|sinx|,x∈[0,2π]的图象与直线y=k有且仅有两个不同的交点,则k的取值范围为(1,3).
以上五个命题中正确的有____(填写所有正确命题的序号)
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答案(点此获取答案解析)

①②

同类题5

阅读下列短文,从每题所给的A、B、C、D四个选项中选出最佳选项。

C

    "Tom? Are you in bed yet?" called Mrs. White. There was no answer. Mrs. White put down her book and went to her 14-year-old son's room. Tom was sitting in front of a bright computer screen on which a motorbike was running fast.

    "Oh, Tom. You're still playing on that computer game. You must stop now, because it's half past eleven. If you don't go to bed soon, you'll be very tired tomorrow." Said Mrs. White.

    "But I've nearly won the game." Tom said to Mrs. White. She could see the excitement on his face. She sat beside him.

    "You're always playing on the computer. You spend more time on this machine than on your homework."  

    Today more and more families have computers. Parents hope computers can help their children improve their study at school. But many of their children use computers to play games, listen to songs and watch videos instead of studying. We often see that computer net bars are crowded with people, especially young boys. They spend a lot of money competing with the computerized machines. The more they lose, the more they want to win. The result is that they don't want to work or study.

    In some countries, even scientists hate computers. They say computers cause millions of people to lose their jobs or cause them a lot of trouble. Computer game addiction(瘾) is a serious problem in social life. Something should have to be done to solve the problem.