English: A diagram showing some basic properties of an ellipse, including
*The distance to a focus, F, from the centre C, is the eccentricity, e multiplied by the semimajor axis, a. *The distance from one focus to the other via any point on the ellipse, P, is always 2a. *The distance from a point, P, on the ellipse to a focus is always proportional to the distance to a vertical line, D, called the directrix. The constant of proportionality is the eccentricity, e. *The eccentricity is always between 0 and 1. At zero, the ellispe becomes a circle, at 1 the ellipse becomes a parabola. Greater than one, it is a hyperbola.

Ellipse properties> e=0.8 , a=170 px , b=102 px , f=e*a=136 px , d=a/e=212.5 px , Origin = (0 px,0 px)
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