[obm-l] USA math olympiad

[Luís Lopes <qed_texte@xxxxxxxxxxx>]

Sauda,c~oes,

Recebi agora de uma outra lista.

[]'s
Luis

This question was on today's USA math olympiad. Enjoy.


Let ABCD be a quadrilateral, and let E and F be points on AC and BC,
respectively, such that AE/ED = B/FC. Ray FE meets rays BA and CD at
S and T, respectively. Prove that the circumcircles of SAE, SBF, TCF,
and TDE pass through a common point.

A neat schema.

Steve Sigur

Triangle web page:
http://paideiaschool.org/TeacherPages/Steve_Sigur/geometryIndex.htm

Other math:
http://paideiaschool.org/TeacherPages/Steve_Sigur/interesting2.htm


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