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 ========================================================================= Instruções para entrar na lista, sair da lista e usar a lista em http://www.mat.puc-rio.br/~nicolau/olimp/obm-l.html =========================================================================