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MathNet 2017-part-06 — 176 problems (EN–VI) Question 169

Math Olympiad Vault · MathNet 2017-part-06 — 176 problems (EN–VI)

Question 169

The diagonals of convex quadrilateral $ABCD$ meet at point $E$. Given
$$
\frac{|AB|}{|CD|} = \frac{|BC|}{|AD|} = \sqrt{\frac{|BE|}{|DE|}}
$$
show that $ABCD$ is either a parallelogram or a cyclic quadrilateral.