题干

已知曲线C的极坐标方程是ρ=2,以极点为原点,极轴为x轴的正半轴建立平面直角坐标系,直线l的参数方程为 {x=1+ty=3t (t为参数).
(Ⅰ)写出直线l的普通方程与曲线C的直角坐标方程;
(Ⅱ)设曲线C经过伸缩变换 {x'=xy'=
1
2
y
得到曲线C',若点P(1,0),直线l与C'交与A,B,求|PA|•|PB|,|PA|+|PB|.
上一题 下一题 0.0难度 选择题 更新时间:2013-01-21 05:30:13

答案(点此获取答案解析)

解:(Ⅰ)C的普通方程为x2+y2=4,l: y=3(x1)
(Ⅱ)根据条件可求出伸缩变换后

同类题2

阅读理解

(Q = Question; A = Answer)

    Situation I

    Q: If someone sits right next to me in an empty movie theater, is it rude to move?

    A: Maybe, but nobody will fault you for it. Chances are that close sitter doesn't realize he disturbs you, so he may miss your annoyance. You undoubtedly aren't the first person he's met who needs enough room. Forgive his bad judgment, move quietly and enjoy the show.

    Situation II

    Q: If I use the bathroom at a store, do I need to buy something?

    A: Consider frequency and urgency. Is this a one-time or an emergency? If so, you don't have to buy anything, but it would be kind if you did. However, if you regularly use the bathroom at this place, then you are a customer, and you should act like one.

    Situation III

    Q: If someone is talking loudly on the bus, is there a nice way to ask him to keep it down?

    A: No. Try other means.1) Stare at him until he gets aware of it and quiets down. 2) Lift your finger in a silence motion(动作)and smile. 3) Put on earphones and ignore him.

    Situation IV

    Q: If I remember my friend's birthday a day late, should I apologize or just wish her a happy birthday like nothing happened?

    A: This is the reason why the word belated was invented. "Happy belated birthday!" is short for: "Well, I know I forgot, but then I remembered. Forgive me and happy birthday."

    Situation V

    Q: Can I lie about seeing a text because I was too busy or lazy to respond(回复) to it?

    A: Don't lie. Receiving a text does not mean you need to respond to it. Why waste a perfectly good lie when the truth will serve? "Yes," you can say if ever asked, "I saw it." No explanation is needed as to why you don't respond.