题干

如图,点P在平面上从点A出发,依次按照点B、C、D、E、F、A的顺序运动,其轨迹为两段半径为1的圆弧和四条长度为1,且与坐标轴平行的线段.设从运动开始射线OA旋转到射线OP时的旋转角为α.若点P的纵坐标y关于α的函数为f(α),则函数f(α)的图象(   )

A:关于直线 α=π4 成轴对称,关于坐标原点成中心对称

B:关于直线 α=3π4 成轴对称,没有对称中心

C:没有对称轴,关于点(π,0)成中心对称

D:既没有对称轴,也没有对称中心.

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答案(点此获取答案解析)

D

同类题1

阅读下面短文,根据其内容,从方框中选择适当的单词填在标有题号的空白处,使语意通顺、完整.(每空一词,切不可重复使用)

moving    direction    fall      hands      where    protect     yourself

against    as        up     possible     easily     them  thing   ground

 What should you do if you are in a crowd(人群)? The first and most important ____   is to make yourself clear where you are and where the exits are. No matter ____  you are, make sure you always know how to get out and to be safe.

 Make yourself know the type of  ____  you are standing on. Wet or uneven(不平坦的)ground can cause you to ____  down in a crowd of moving people.

 If you find ____   in the middle of a moving crowd, you must be careful. Do not walk ____  the moving direction and do not stop or sit down, because you could get trampled (踩踏)  ____ Instead, move in the same ____  of the crowd. Keep your____  up by your chest(胸部)to protect your chest. If you fall down, get up quickly, If you can't get  ____  , ask someone to pull you back up. If you have kids, lift  ____  up.

 If you fall and cannot get up, keep on  ____   in the same direction of the crowd. If that is not  ____   , then cover your head with your arms.

 Try to get away from hard things in a crowd. If you're pushed against them, ____   a result, you may be hurt badly.

 We should learn to ____  ourselves. Stay away from the crowd.

Remember: Whatever you do, safety is first!