问题
填空题
圆C：ρ=4Sinθ的圆心C到直线l：
|
答案
由圆C：ρ=4Sinθ得ρ2=4ρsinθ，化为x2+y2=4y，即x2+（y-2）2=4，∴圆心C（0，2），半径r=2．
把直线l：
(t为参数)的参数t消去得x+y=6．x=3+t y=3-t
∴圆心C（0，2）到直线l的距离d=
=2|0+2-6| 2
．2
故答案为2
．2
搜题请搜索小程序“爱下问搜题”
圆C：ρ=4Sinθ的圆心C到直线l：
|
由圆C：ρ=4Sinθ得ρ2=4ρsinθ，化为x2+y2=4y，即x2+（y-2）2=4，∴圆心C（0，2），半径r=2．
把直线l：
(t为参数)的参数t消去得x+y=6．x=3+t y=3-t
∴圆心C（0，2）到直线l的距离d=
=2|0+2-6| 2
．2
故答案为2
．2
Do you often feel tired or hard to concentrate(集中精力) in class ? If your answers to this question is yes, 小题1: . .Not getting enough sleep can lead to many kinds of problems. New studies show that not only Chinese students suffers from lack(不足) of sleep，American students also have the same problem . 小题2: Why are they so tired ? One big reason is the use of electronic products（电子产品）. A recent survey finds out that 71% of American kids aged 8 to 18 have TVs in the rooms and about 36% have computers in their rooms. 小题3: , playing video games ,sending text messages to friends and watching TV before bedtime. How to solve the problem ? Scientist advise “ 小题4: . ”Spending more time on sleep can help students stay healthy 小题5: 根据以上内容，从下 * * 个选项中选择适当的句子还原到短文中，使短文完整与正确。将其标号在答题卡上涂黑。（每小题2分，共10分）
|