Focal Definition of Ellipse

The applet below illustrates the focal property of the ellipse: given two points F and F' (called the foci of the ellipse), ellipse is the locus of points P the sum of whose distances to the foci is constant: PF + PF' = const. This property is often taken for a definition of ellipse. (A different demonstration can be found elsewhere.)

 

This applet requires Sun's Java VM 2 which your browser may perceive as a popup. Which it is not. If you want to see the applet work, visit Sun's website at https://www.java.com/en/download/index.jsp, download and install Java VM and enjoy the applet.


What if applet does not run?
 

Conic Sections > Ellipse

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