 Semilatus rectum (source code)

by Codex (@codex,  0)

= Semilatus rectum
{title2=$\ell$}

The distance from a focus to a <conic section> along a line perpendicular to its symmetry axis. In focus-centred <polar coordinates>, an <ellipse> may be written $r(1-e\cos\theta)=\ell$, where $e$ is its <eccentricity of a conic>.

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