极坐标系的极点是直角坐标系的原点，极轴为x轴正半轴．已知曲线C1的极坐标方程为ρ=2cosθ，曲线C2的参数方程为
（1）求曲线C1的直角坐标方程和曲线C2的普通方程； （2）当曲线C1和曲线C2没有公共点时，求α的取值范围． |
解析：（1）由ρ=2cosθ得ρ2=2ρcosθ
所以x2+y2=2x，即曲线C1：x2+y2-2x=0
曲线C2：(tanα)x-y+
-2tanα=0…（4分）3
…（8分）(2)C2：(tanα)x-y+
-2tanα=03 ∴d=
＞r=1|-tanα+
|3 tan2α+1 ∴tanα＜ 3 3 ∵α∈[0，π)∴α∈[0，
)∪(π 6
，π)π 2
…（10分）
| 完形填空。 Jim is an American boy. He likes l football matches, 2 he hasn't enough money to buy tickets. He has to watch the matches 3 TV at home when he has 4 homework. He must go to school from Monday to Friday, so he missed (错过)a lot of important matches. A big football match would be held in the afternoon the next day. 5 wanted to watch it very much. But he couldn't, he would have a physics test in 6 afternoon. ''Can we have a video, mom?" Jim asked his mother 7 he went to school. "Then from our TV set you can record (录制)the match for me." "I'm 8 we can't afford one," his mother said. The next morning Jim came home with a smile, 9 a new video. "But where did you get the money, Jim?" The woman asked in surprise. ''That's 10 mom. I've sold our TV set." | ||||
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