2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/128736In a couple of articles (Ford G W and O'Connell R F 1996 Nature 380 113 and 2002 J. Phys. A: Math. Gen. 35 4183) it was argued that the standard result for the derivative of the hyperbolic cotangent in the literature, d \coth y/dy = -{csch}^2 y is incomplete and the correct expression should have an additional term proportional to the Dirac delta function. The purpose of this paper is to demonstrate that this claim is incorrect.Quantum Physicstext