Abstract <p>For the equation of beam vibration, taking into account its rotational motion during bending, the inverse problems of finding the right-hand side, i.e., the source of vibrations, are studied. When substantiating the existence of a solution to the inverse problem of determining the multiplier of the right-hand side, depending on the spatial coordinate, the problem of small denominators arises. In this regard, estimates of the denominators are established, guaranteeing their separation from zero, indicating the corresponding asymptotics. Based on these estimates, the convergence of the series in the class of regular solutions of the beam oscillation equation is substantiated.</p>