Distance from conic-section point to focus divided by distance from conic-section point to directrix is constant {eccentricity, conic}: e = (a^2 + b^2)^0.5 / a, where a is major axis and b is minor axis. For circle, e = 2^0.5. For parabola, e = 1, because b = 0. For hyperbola and ellipse, e > 1.
Mathematical Sciences>Geometry>Solid>Cone>Conic Section>Eccentricity
3-Geometry-Solid-Cone-Conic Section-Eccentricity
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Date Modified: 2022.0224