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MathNet 2015-part-06 — 191 problems (EN–VI) Question 182

Math Olympiad Vault · MathNet 2015-part-06 — 191 problems (EN–VI)

Question 182

In the convex quadrilateral $ABCD$ the angles $ABC$ and $BCD$ are equal to $120^\circ$, $O$ is the intersection of the diagonals, $M$ is the midpoint of $BC$, and $K$ is the point of intersection of $MO$ and $AD$. It happens that $\angle BKC = 60^\circ$. Prove that $\angle BKA = \angle CKD = 60^\circ$.

(Serduk Nazar)