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isosceles wanted, AB = AH, CG = CB, ABCD # (2017 NZOMC Camp Sel. p2)

Source:

January 10, 2021
geometryisoscelesparallelogramequal segments

Problem Statement

Let ABCDABCD be a parallelogram with an acute angle at AA. Let GG be the point on the line ABAB, distinct from BB, such that CG=CBCG = CB. Let HH be the point on the line BCBC, distinct from BB, such that AB=AHAB = AH. Prove that triangle DGHDGH is isosceles.
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