The proof is an immediate consequence of the basic figure for the construction of harmonic conjugate points discussed in Harmonic.html . By the discussion there we know that points P, G are harmonically conjugate to B, D and points P, H harmonically conjugate to A, C hence the definition of the polar applies for line [EF]. This procedure of constructing the polar works also for conics. The preceding proof transfers verbatim to that case.

For a further property of the polar, concerning the duality of the correspondence pole <--> polar see the file Polar3.html .

Polar.html

Polar3.html

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