Tracing Out An Ellipse Using the Sum-of-The-Distances Definition
If the animation does not appear, click
here.
This animation shows how to use the sum-of-the-distances definition of ellipse to trace out
such a curve.
(See notes below.)
The horizontal line segment shown below the curve consists
of a copy of the blue segment that connects the left-hand focus with the moving
point on the ellipse and a copy of the red segment that connects the right-hand
focus with the moving point; as the moving point traces out the curve,
the sum of the two lengths
remains constant.
A similar figure, colored differently, lies in the plane
that appears in the
Dandelin construction,
The Dandelin construction and the sum-of-the-distances definition of ellipse,
for the ellipse.
Return to the Geometry of the Conic Sections page.