2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/156191In this paper we will show that using the cosmological constant as a new thermodynamical state variable, the differential and integral mass formulas of the first law of thermodynamics for asymptotic flat spacetimes can be extended to (2+1) dimensional charged BTZ black holes and charged de Sitter space.4 pagesGeneral Relativity and Quantum Cosmologytext