The

The proof is essentially the same as the one given in the above reference. We consider the bundles of lines A(W

A special case arises when D tends to coincide with A. In that case DA becomes a tangent to the conic and the theorem of Desargues beomes a property of triangles inscribed in conics. This is discussed in DesarguesInvolution2.html .

The theorem of Desargues transfers with the same wording to conics defined in the complex projective space. There every two conics have four intersection points and the arguments transfer verbatim. A consequence of the validity of the theorem in the complex case is demonstrated in the file DesarguesInvolutionComplex.html .

DesarguesInvolution2.html

DesarguesInvolution3.html

DesarguesInvolutionComplex.html

FourPtsAndTangent.html

FourPtsAndTangent2.html

HomographicRelation.html

HomographicRelationExample.html

InvolutionBasic.html

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