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CGMO 2003 Problem 7

    Let the sides of a scalene triangle △ABC\triangle ABC be AB=c,AB = c, BC=a,BC = a, CA=b,CA =b, and D,E,FD, E , F be points on BC,CA,ABBC, CA, AB such that AD,BE,CFAD, BE, CF are angle bisectors of the triangle, respectively. Assume that DE=DF.DE = DF. Prove that

    (1) ab+c=bc+a+ca+b\frac{a}{b+c} = \frac{b}{c+a} + \frac{c}{a+b}

    (2) ∠BAC>90∘.\angle BAC > 90^{\circ}.

    Dataset text AI-MO AoPS. Quoted with source.

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