Bodenmiller theorem

Consider a complete quadrilateral with four sides $a$, $b$, $c$, $d$ intersecting in the six points $P$, $Q$, $R$, $S$, $T$, $U$. Then the three circles that have the three diagonals $PS$, $QT$ and $RU$ as diagonals intersect in the same two points.

<img style="border:1px solid;" src="https://www.encyclopediaofmath.org/legacyimages/common_img/b110680a.gif" />

Figure: b110680a

References

[a1]	R. Fritsch, "Remarks on Bodenmiller's theorem" J. of Geometry , 47 (1993) pp. 23–31
[a2]	G. Weiss, "Eine räumliche Deutung der Vierseiteigenschaft von Bodenmiller" Elemente der Math. , 37 (1982) pp. 21–23

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