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MathNet 2023-part-05 — 191 problems (EN–VI) Question 30

Math Olympiad Vault · MathNet 2023-part-05 — 191 problems (EN–VI)

Question 30

The triangle $ABC$ has $\angle BAC = 90^\circ$ and $\angle ABC = 60^\circ$. The points $D$ and $E$ are taken on the sides $AC$, respectively $AB$, so that $CD = 2 \cdot DA$ and $DE$ is the bisector of the angle $\angle ADB$. Denote $M$ the intersection of the lines $CE$ and $BD$, and $P$ the intersection of the lines $DE$ and $AM$. Prove that:

a) the lines $AM$ and $BD$ are perpendicular;

b) $3 \cdot PB = 2 \cdot CM$.