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MathNet 2011 Question 70

Math Olympiad Vault · MathNet 2011

Question 70

Let $ABCD$ be a convex quadrilateral such that $\angle ADB = \angle BDC$. Suppose that a point $E$ on the side $AD$ satisfies the equality
$$
AE \cdot ED + BE^2 = CD \cdot AE.
$$
Show that $\angle EBA = \angle DCB$.