Li 2(1)=pi^2/6
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Theorem
The following formula holds: $$\mathrm{Li}_2(1) = \dfrac{\pi^2}{6},$$ where $\mathrm{Li}$ denotes the dilogarithm and $\pi$ denotes pi.
Proof
References
1926: Leonard Lewin: Polylogarithms and Associated Functions (2nd ed.) ... (previous) ... (next): (1.9)