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在平面直角坐标系xOy中,以O为极点,x轴的正半轴为极轴建立极坐标系.若直线l的极坐标方程为 2ρcos(θ−π
4
)
−2=0
,曲线C的极坐标方程为:ρsin2θ=cosθ,将曲线C上所有点的横坐标缩短为原来的一半,纵坐标不变,然后再向右平移一个单位得到曲线C1.

(Ⅰ)求曲线C1的直角坐标方程;

(Ⅱ)已知直线l与曲线C1交于A,B两点,点P(2,0),求|PA|+|PB|的值.

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解:(I)曲线C的极坐标方程为:ρsin2θ=cosθ,即ρ2sin2θ=ρcosθ,化为直角坐标方程:y2=x.

将曲线C上所有点的横坐标缩短为原来的一半,纵坐标不变,然后再向右平移一个单位得到曲线C1:y2=2(x﹣1).

(II)直线l的极坐标方程为

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A report by UNEP联合国环境规划署(United Nations Environment Programme) says that by 2050, the world's population is expected to reach 9.6 billion and feeding us all will require at least 60% more food than we have ever produced before. What's more, if we can't find out a way to do with it, food shortages (短缺) could be a big problem.

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