quadrangle ABCD by extending its sides and drawing its diagonals. {E,F,G} are the

of the quadrilateral. The properties of this figure are studied in Quadrangle_0.html .

The figure stresses the fact that all quadrangles resulting from ABCD by the suggested way have alternatively

the same diagonals forming a harmonic bundle at G (see Harmonic_Bundle.html ).

Harmonic_Bundle.html

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