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Prove that AC + CF = AB + BF

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September 1, 2010
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Problem Statement

Points DD and EE are chosen on the sides ABAB and ACAC of the triangle ABCABC in such a way that if FF is the intersection point of BEBE and CDCD, then AE+EF=AD+DFAE + EF = AD + DF. Prove that AC+CF=AB+BF.AC + CF = AB + BF.