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△ABC中，∠C=90°，∠B=60°，AC=3，以C为圆心，r为半径作⊙C，如果点B在圆内，而点A在圆外，那么r的取值范围是______．

答案

因为△ABC中，∠C=90°，∠B=60°，所以∠A=30°，得到AC=

3
BC，又AC=3，得BC=
3
．

∵点B在圆内，∴r＞BC=

3
．

∵点A在圆外，∴r＜AC=3．

因此：

3
＜r＜3．

故答案是：

3
＜r＜3．

阅读理解

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小题1:If you want to get a good sleep, you'd better _______.
A．go to bed after you're triedB．go to sleep at midnight
C．follow the bedtime routineD．eat something or read in bed
小题2:You should visit the dentist at least once a year because_______.
A．the oral examination is necessaryB．you don't often brush your teeth
C．some diseases may be in the mirrorD．you don't have a good night's sleep
小题3:Studies have shown that many diseases have something to do with_______.
A．having no oral examinationB．washing hands with cold water
C．sleeping too late sometimesD．doing little physical activity
小题4:When you want to learn more about the flu, you can_______.
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单项选择题

机器人所表现的任何智能，都是人类智能活动的结果。没有科学家精心编制的程序，没有迅速发展的电广技术，没有精密的机械加工，机器人是不可能表现出任何智能的。由此可知( )。

A．机器人没有智能

B．机器人的智能是人类赋予的

C．机器人智能的发展有可能超过人类

D．机器人在未来有着广泛的用途
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