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MathNet 2015-part-06 — 191 problems (EN–VI) Question 99

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

Question 99

In triangle $ABC$, let $A'$ be the point symmetric to $A$ with respect to the circumcenter $O$ of $ABC$.

a) Prove that the sum of the squares of the tangent segments drawn from $A$ and $A'$ to the incircle of $ABC$ is equal to $4R^2 - 4Rr - 2r^2$.

b) Let $I$ be the incenter of $\triangle ABC$. Prove that the circle with center $A'$ and radius $A'I$ meets the circumcircle of $ABC$ at a point $L$ such that $AL = \sqrt{AB \cdot AC}$.