Why Does This Integral Not Converge?

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SUMMARY

The integral $$\int_{-\infty}^{\infty} \frac{e^{-iax} \coth[\sinh[bx]]}{\sinh[bx]} dx$$ does not converge, as confirmed by Mathematica, which indicates that the integral diverges over the interval from negative to positive infinity. The discussion suggests employing complex analysis techniques, particularly calculating the residue at the pole of order 2 located at z=0, to further analyze the integral's behavior. This approach is essential for understanding the convergence properties of integrals involving hyperbolic functions.

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How to solve $$\int_{-\infty}^{\infty} \frac{e^{-iax}coth[sinh[bx]]}{sinh[bx]} dx$$
mathematica gives the result ::idiv: "Integral of E^(-Iax)\ Coth[Sinh[bx]]\ Csch[bx] does not converge on {-\[Infinity],\[Infinity]}."
thanks!
 
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Hi.
How about trying complex integral. The integrand seem to have a pole of order 2 at z=0. You may calculate residue there.
 

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