题干

如图,已知l1⊥l2,圆心在l1上,半径为1m的圆O在t=0时与l2相切于点A,圆O沿l1以1m/s的速度匀速向上移动,圆被直线l2所截上方圆弧长记为x,令y=sin
2
x
2
,则y与时间t(0≤t≤1,单位:s)的函数y=f(t)的图象大致为(  )

A:

B:

C:

D:

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答案(点此获取答案解析)

B

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    Andy never wanted to go to bed on time. His parents had explained to him how important it was to go to bed early and get a good rest. But Andy paid no attention to them, and they didn't know what to do until one weekend when they were visiting Andy's grandparents.

    Grandpa Peter heard all about it and said, "This sounds like a job for Tubby." So Andy's parents loaded the cat onto the car and returned home.

That night, at bedtime, the same problem happened. Andy didn't want to go to bed, and even though his parents waited a while to see if Tubby would solve the problem, nothing happened.

    Hours later, Andy finally decided to go to bed. But what a surprise when he entered his bedroom! Tubby was in his bed, totally sprawling out, pot-belly in the air, and snoring like an express train.

    Andy tried to move the cat, but there was no way of moving him an inch. That night he hardly slept, lying on one tiny corner of his bed.

    The next day the same thing happened, even though Andy was much more tired from not having slept well. When the third day arrived, he had understood that if he wanted to sleep in his bed, he would have to get into it before Tubby did. That night, when his parents only started to mention the topic of bedtime, Andy rushed upstairs and dived into bed. His parents could not believe it. They knew nothing about Tubby in the bed, nor did they understand why Andy went to bed on time without complaint. They were so happy about this that they stayed up quite late, celebrating.