Latus rectum

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In a conic section, the latus rectum is the chord parallel to the directrix through the focus, with the symbol 2l. In a parabola, the length of the latus rectum is equal to four times the focal length. In an ellipse, it is twice the square of the length of the semiminor axis b divided by the length of the semimajor axis \frac{2b^2}{a}. In a hyperbola, it is twice the square of length of the conjugate axis divided by the length of the transverse axis. In a circle, the latus rectum is always the length of the diameter. In polar coordinates, \frac{l}{r} = 1 + \varepsilon \cos(t) where \varepsilon is eccentricity. This is Newtonian form depicting planetary orbits as per Kepler's Laws.

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