Invariant reciprocal area sum for lateral harmonic polygons

Let H\mathcal{H} be a Poncelet family of NN-gons interscribed between two homothetic, concentric ellipses, and let A1A_1 and A2A_2 be the areas of the two lateral harmonic polygons obtained as polar images with respect to circles centered at the two foci of the inner ellipse. Lateral-area invariant conjecture. For any odd NN, the quantity

1A1+1A2\frac{1}{A_1}+\frac{1}{A_2}

is invariant. The formula is proved for N=3N=3 and N=5N=5, while the assertion for every odd NN is presented experimentally and remains open.

Sources & referencesView supporting material

Primary source

Ronaldo Garcia, Dan Reznik and Pedro Roitman, “New Properties and Invariants of Harmonic Polygons”, arXiv:2112.02545 (2022).

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