Ellipse_caustic

Elliptical caustic

Given is a fixed point A and a point C moving on a fixed ellipse. For each position of C we consider the symmetric B of A, with respect to the normal of the ellipse at C. We consider also the line CB, symmetric of AC, with respect to the normal.

For C moving on the ellipse, the geometric locus of point B is the red line (omothetic with ratio 2 of the [normal pedal] of A with respect to the ellipse). The envelope of lines BC is called [caustic] of the ellipse, with respect to the point A.

For a picture of the pedals (tangential and normal) of the ellipse, look at the file: Pedals.html .

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