Semi-major and semi-minor axes
= Semi-major and semi-minor axes
{title2=$a,b$}
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The <semi-major and semi-minor axes> are the larger and smaller half-axis lengths of an <ellipse>. In principal-axis coordinates the <ellipse> has equation $x^2/a^2+y^2/b^2=1$ with $a\ge b>0$. The same terminology is used for a <hyperbola> $x^2/a^2-y^2/b^2=1$, where $a$ is half its transverse axis and $b$ half its conjugate axis. Orbital semiaxes apply these geometric quantities to <conic sections>.