In our school library there a number of books on science, and in these years the number of them growing larger and larger.
A:are; is
B:is; are
C:have; are
D:has; is
春秋第一霸主是楚庄王。
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利率是表示( )的比值.
在极坐标系中,已知圆C的圆心C(2,π4),半径r=3.
(Ⅰ)求圆C的极坐标方程;
(Ⅱ)若α∈0,π4),直线l的参数方程为x=2+tcosαy=2+tsinα(t为参数),直线l交圆C于A、B两点,求弦长|AB|的取值范围.
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