题干

(坐标系与参数方程选做题)在极坐标系中,直线ρ(cosθ﹣sinθ)+2=0被曲线C:ρ=2所截得弦的中点的极坐标为____ 

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(2,π
3
4
)

同类题2

    America is a mobile society. Friendships between Americans can be close and real, yet disappear soon. They don't feel hurt. If the same two people meet again, even years later, they pick up the friendship. This can be quite difficult for us Chinese to understand .Friendships between us develop more slowly but may become lifelong feelings, extending(延伸)deeply into both families.
T    here is another difficult point for us to understand. Although Americans treat friends warmly in their personal everyday lives, they don't show their politeness to them if it requires a great deal of time. But in China, we are usually generous with our time. We, as hosts, will appear at an airport even in the middle of the night to meet a friend. We may take a day off from our work to act as guides to our friends. It is opposite in America. Americans cannot manage the time to do a great deal with a visitor outside their daily plans. They will probably expect the visitors to get themselves from the airport to the hotels. And they expect the visitors will phone them from there. Once the visitors arrive at their homes, the welcome will be full, warm and real.
    For Americans, it is often considered more friendly to invite a friend to their homes than to restaurants, except for business matters. Americans are ready to receive us foreigners at their homes, share their holidays, and their home life. So accept their hospitality(好客)at home and enjoy your visit in America!