• 曲线和方程 圆的方程如图,设P(x,y),则M(2x,0),N(0,2y).因为AM⊥AN,则有k AM·k AN=-1,即 ...t2=(x0-c)2+y02 ③①+②得2x02+2y02+2t2=2r2即x02+y02+t2=r2 ④...
  • CORE Discussion Paper #2009/382In this semi-parametric specification we do not control for countries fixed...(N(T 1))1/2y′nparQ ynpar0,2πσ4with Q = P′pD′testDtestPp D′testDtest ...
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