Selecting the projective base as indicated, the equation of the conic (v) becomes v = xy-z

The same argument applies to

[1] The above figure displays also conic v'' tangent to the pair of lines {QS, PR}. The lemma, in most cases, is applied to prove the existence of conics (like v', v'') tangent to the degenerate members of family I(w,xy).

[2] As seen from the proof, the arguments for the degenerate member-conic mn of I(w,xy) can be restricted to real conics. For more general members of the family I(w,xy) though, one has to work in the complex projective plane.

[3] Hart's lemma is the building block of Hart's proof, of

Poncelet_Proof.html

Poncelet.html

ProjectiveBase.html

ProjectiveCoordinates.html

ProjectivePlane.html

Berger, M

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