Summary: In this paper it is shown that under specified conditions on the initial data a certain infinite coupled system of ordinary differential equations has a solution satisfying an auxiliary convergence condition. The infinite system discussed is essentially the Galerkin expansion of the solution to a given quasi-linear e equation. The results obtained suffice to prove the existence of a solution to this equation of oscillations of a beam.

Keywords: quasi-linear wave equation, method of energy inequalities, equation of oscillations of a beam.