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CAPS 2009 Problem 3

    Let ω\omega denote the excircle tangent to side BCBC of triangle ABCABC . A line ℓ\ell parallel to BCBC meets sides ABAB and ACAC at points DD and EE , respectively. Let ω′\omega' denote the incircle of triangle ADEADE . The tangent from DD to ω\omega (different from line ABAB ) and the tangent from EE to ω\omega (different from line ACAC ) meet at point PP . The tangent from BB to ω′\omega' (different from line ABAB ) and the tangent from CC to ω′\omega' (different from line ACAC ) meet at point QQ . Prove that, independent of the choice of ℓ\ell , there is a fixed point that line PQPQ always passes through.

    Dataset text AI-MO AoPS. Quoted with source.

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