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MathNet 2019-part-06 — 184 problems (EN–VI) Question 12

Math Olympiad Vault · MathNet 2019-part-06 — 184 problems (EN–VI)

Question 12

Let $AD$ be the altitude of the right angled triangle $ABC$ with $\angle A = 90^{\circ}$. Let $DE$ be the altitude of the triangle $ADB$ and $DZ$ be the altitude of the triangle $ADC$ respectively. Let $N$ be chosen on the line $AB$ such that $CN$ is parallel to $EZ$. Let $A'$ be the symmetric of $A$ with respect to the line $EZ$ and $I, K$ the projections of $A'$ onto $AB$ and $AC$ respectively. Prove that $\angle NA'T = \angle ADT$, where $T$ is the intersection point of $IK$ and $DE$.