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MathNet 2020 — Math Olympiad Vault — Part 03 Question 40

Math Olympiad Vault · MathNet 2020 — Math Olympiad Vault — Part 03

Question 40

Let $\Gamma$ be a circle of radius $1$ centered at $O$. A circle $\Omega$ is said to be friendly if there exist distinct circles $\omega_{1}, \omega_{2}, \ldots, \omega_{2020}$, such that for all $1 \leq i \leq 2020$, $\omega_{i}$ is tangent to $\Gamma$, $\Omega$, and $\omega_{i+1}$. (Here, $\omega_{2021}=\omega_{1}$.) For each point $P$ in the plane, let $f(P)$ denote the sum of the areas of all friendly circles centered at $P$. If $A$ and $B$ are points such that $OA=\frac{1}{2}$ and $OB=\frac{1}{3}$, determine $f(A)-f(B)$.