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Ramanujan Cos/Cosh Identity


\begin{displaymath}
\left[{1+2\sum_{n=1}^\infty {\cos(n\theta )\over \cosh(n\pi)...
...)}}\right]^{-2} = {2\Gamma^4({\textstyle{3\over 4}})\over \pi}
\end{displaymath}

for all $\theta$, where $\Gamma(z)$ is the Gamma Function.




© 1996-9 Eric W. Weisstein
1999-05-25