Analytic Continuation of Riemann Zeta Function using Dirichlet Eta Function

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Theorem

Let $\zeta$ be the Riemann zeta function.

Let $\eta$ be the Dirichlet Eta Function.


Then:

$\dfrac 1 {1 - 2^{1 - s} } \map \eta s$

defines an analytic continuation of $\zeta$ to the half-plane $\map \Re s > 0$ minus $s = 1$.


Proof

By Riemann Zeta Function in terms of Dirichlet Eta Function, it coincides with $\zeta$ for $\map \Re s > 1$.

By Dirichlet Eta Function is Analytic, it is analytic for $\map \Re s > 0$, except at $s = 1$.

$\blacksquare$


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