Problem

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Tags: IGO, geometry



let H the orthocenter of the triangle ABC pass two lines l1 and l2 through H such that l1l2 we have l1BC=D and l1AB=Z also l2BC=E and l2AC=X like this picture pass a line d1 through D parallel to AC and another line d2 through E parallel to AB let d1d2=Y prove X , Y and Z are on a same line


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