单词 | parabola |
释义 | parabola A conic with eccentricity e = 1 . It is the locus of a point that moves so that its distance from the focus is equal to its perpendicular distance from the directrix . A chord through the focus, perpendicular to the axis, is called the latus rectum . For a parabola with its vertex at the origin, lying symmetrically about the x-axis, the equation is y2 = 4ax , where a is the distance from the vertex to the focus. The directrix is the line x = -a , and the latus rectum is 4a. See illustration. ![]() A parabola |
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