2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/216157Using Lie symmetry methods for differential equations we have investigated the symmetries of a Lagrangian for a plane symmetric static spacetime. Perturbing this Lagrangian we explore its approximate symmetries. It has a non-trivial first-order approximate symmetry.5 pagesGeneral Relativity and Quantum Cosmologytext