The involution f is uniquely determined by the two pairs of points (X

This property is obtained as a special case of Desargues Involution theorem (see DesarguesInvolution.html ), in which we identify two points out of the four {A,B,C,D} involved in the original theorem. In the above figure this is done for A and D.

In the above figure I construct the variable conic (c) tangent to (t) at A and passing through B and C, using the bundle of circles generated by the two circles on diameters X

A further special case of this case of Desargues Involution theorem is obtained by letting B coincide with C. This is discussed in DesarguesInvolution3.html .

DesarguesInvolution.html

DesarguesInvolution3.html

FourPtsAndTangent.html

FourPtsAndTangent2.html

HomographicRelation.html

HomographicRelationExample.html

Involution.html

InvolutionBasic.html

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