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MathNet 2005 — Part 03 Question 38

Math Olympiad Vault · MathNet 2005 — Part 03

Question 38

Let $ABC$ be an isosceles triangle such that $AB = AC$ and $\angle \frac{A}{2} \lt \angle B$. On the extension of the altitude $AM$ we get the points $D$ and $Z$ such that $\angle CBD = \angle A$ and $\angle ZBA = 90^{\circ}$. $E$ is the foot of the perpendicular from $M$ to the altitude $BF$ and $K$ is the foot of the perpendicular from $Z$ to $AE$. Prove that $\angle KDZ = \angle KBD = \angle KZB$.