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MathNet 2020 — Math Olympiad Vault — Part 03 Question 5

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

Question 5

Regular hexagon $P_{1} P_{2} P_{3} P_{4} P_{5} P_{6}$ has side length $2$. For $1 \leq i \leq 6$, let $C_{i}$ be a unit circle centered at $P_{i}$ and $\ell_{i}$ be one of the internal common tangents of $C_{i}$ and $C_{i+2}$, where $C_{7}=C_{1}$ and $C_{8}=C_{2}$. Assume that the lines $\{\ell_{1}, \ell_{2}, \ell_{3}, \ell_{4}, \ell_{5}, \ell_{6}\}$ bound a regular hexagon. The area of this hexagon can be expressed as $\sqrt{\frac{a}{b}}$, where $a$ and $b$ are relatively prime positive integers. Compute $100a+b$.