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焦半径定义:连结圆锥曲线(包括椭圆,双曲线,抛物线)上一点与对应焦点的线段的长度,叫做圆锥曲线焦半径.在解析几何中有关焦半径有下列三个结论.(1)已知椭圆x2a2+y2b2=1(a>b>0)的左、右焦点分别是F1(-c,0)、F2(c,0),P是椭圆上的动点,设x为点P的横坐标,则|PF1|=a+c a x,|PF2|=aca x且a-c≤|PF|≤a+c.(2)已知双曲线x2a2-y2b2=1(a>0,b>0)的左、右焦点
Coke Radius Definition: The length of the line segment connecting the conic (including the ellipse, hyperbola, and parabola) and the corresponding focal point is called the conic radius of curvature. There are three conclusions about the coke radius in the analytic geometry: (1) Known The left and right focal points of the ellipse x2a2 + y2b2 = 1 (a> b> 0) are F1 (-c, 0) and F2 (c, 0) respectively. P is the moving point on the ellipse, PF1 | = a + cax, | PF2 | = aca x and ac≤ | PF | ≦ a + c. (2) It is known that the hyperbola x2a2-y2b2 = 1 (a> 0, b> 0) Left and right focus