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Basel time!

Calculus Level 2

\[ \Large \sum_{n=1}^\infty \frac1{n^2} = \ ? \]

\[ \frac \pi e \] \[ \sqrt 2 \pi \] \[ \frac{ \pi^2}6 \] \[ \frac{ \pi^2}4 \]

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Excel in math and science

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It's hard to learn from lectures and videos

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including olympiad champions, researchers, and professionals.

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by Akash Einstein

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