Ellipse
= Ellipse
{wiki}
An ellipse is the locus of points whose distances from two fixed foci have constant sum. If the focal distance is $d$ and the sum is $c>d$, its semimajor and semiminor axes are $c/2$ and $\sqrt{c^2-d^2}/2$.
= Ellipse
{wiki}
An ellipse is the locus of points whose distances from two fixed foci have constant sum. If the focal distance is $d$ and the sum is $c>d$, its semimajor and semiminor axes are $c/2$ and $\sqrt{c^2-d^2}/2$.