问题
填空题
⊙O的直径为20，弦AB=8，P是弦AB上的一个动点，则OP的取值范围是______．
答案
最大为半径：20÷2=10；
最小为弦心距：8÷2=4，
弦心距=
=2102-42
，21
所以OP的取值范围是2
≤OP≤10．21
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⊙O的直径为20，弦AB=8，P是弦AB上的一个动点，则OP的取值范围是______．
最大为半径：20÷2=10；
最小为弦心距：8÷2=4，
弦心距=
=2102-42
，21
所以OP的取值范围是2
≤OP≤10．21
| 完形填空。 | |||
| More and more people are becoming interested in the internet. They have formed a bad habit. In fact, the bad habit has become a 1 -Internet Addiction Disorder (IAD网络综合症). Staying 2 for more than six hours a day 3 working or studying, and feeling very upset from not being able to get online, are the two major symptoms (症状) of IAD. Internet addiction (上瘾) is 4 in China now. A recent research 5 that 42% of Chinese young people get quite interested in the web, while only 18% of Americans feel in the same 6 . What causes IAD? Some people believe that It's the lack (缺乏) of family care. Most children in China are the 7 ones in their families. They are only told to 8 hard, but few really care about their personal interest. So some children would like to keep 9 away from the real world. How can people stay away from IAD? Don t get online any more, go back to the real world and if it doesn't work, go to see the 10 . | |||
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