MathDB
BD=CD+AE wanted, equilateral and parallel to side related

Source: Champions Tournament (Ukraine) - Турнір чемпіонів - 2016 Seniors p3

September 3, 2020
geometryequal segmentsEquilateralChampions Tournament

Problem Statement

Let tt be a line passing through the vertex AA of the equilateral ABCABC, parallel to the side BCBC. On the side ACAC arbitrarily mark the point DD. Bisector of the angle ABDABD intersects the line ttat the point EE. Prove that BD=CD+AEBD=CD+AE.
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