Eccentricity and shape of the ellipse

The eccentricity $e = c/a$ is the number that governs the shape of the ellipse, independently of its size. For a fixed semi-major axis $a$, changing $e$ takes us from an almost circular figure to a very elongated one.

Three ellipses with the same semi-major axis $a$ but different eccentricities: the smaller $e$ is, the “rounder” the ellipse; the closer $e$ gets to $1$, the more the ellipse flattens.

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Topics: Ellipse
Concepts: Circle · Eccentricity · Ellipse
Skills: Interpreting a graph · Plotting a graph