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• 549 How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?
• 176 What's 4 times more likely than 80%?
• 139 Slice of pizza with no crust
• 124 How to prove that $\frac{\zeta(2) }{2}+\frac{\zeta (4)}{2^3}+\frac{\zeta (6)}{2^5}+\frac{\zeta (8)}{2^7}+\cdots=1$?
• 118 Parabola is an ellipse, but with one focal point at infinity
• 106 How to sum this series for $\pi/2$ directly?
• 83 Proving an alternating Euler sum: $\sum_{k=1}^{\infty} \frac{(-1)^{k+1} H_k}{k} = \frac{1}{2} \zeta(2) - \frac{1}{2} \log^2 2$
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