= Prolate spheroid
{title2=$c>a=b$}
A <prolate spheroid> is an <ellipsoid> with two equal shorter semiaxes and a longer symmetry-axis semiaxis. Its meridional section is an <ellipse> rotated about its major axis. In the coordinates $R^2/(\lambda+\alpha)+z^2/(\lambda+\beta)=1$ with $\beta>\alpha$, a fixed regular $\lambda$ has equatorial radius $\sqrt{\lambda+\alpha}$ and polar radius $\sqrt{\lambda+\beta}$; its focal separation is independent of $\lambda$, giving a confocal family.
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