A two-sided inequality for the zeta function, digamma function, and cotangent

From papers

Let B1(x)B_1(x) be the first Bernoulli polynomial, let ψ\psi denote the digamma function, and let γ=ψ(1)\gamma=-\psi(1) be the Euler–Mascheroni constant. Define

b:=B1(γ)=γ+12,b:=B1(γ)=γ12.\overline{b}:=\overline{B_1(\gamma)}=\gamma+\frac{1}{2},\qquad b:=B_1(\gamma)=\gamma-\frac{1}{2}.

For 0<x<10<x<1, the inequality conjecture.

πcot(πx)+x<ζ(x)ψ(x)<πcot(πx)+bx+b.\pi\cot(\pi x)+x<\zeta(x)-\psi(x)<\pi\cot(\pi x)+\overline{b}x+b.

This inequality would give a simple comparison between the Euler–Riemann zeta function, the digamma function, and the cotangent on the unit interval. The source presents it as a problem arising from the study of a related theorem; no resolution is supplied here.

Progress summary

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Sources & referencesView supporting material

Primary source

Michael Andrew Henry, “A simple inequality relating the Euler-Riemann zeta function, digamma, and cotangent over the unit interval”, arXiv:2601.00631 (2026).

Solutions 0

No solutions have been posted yet.