2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198791Using the coset construction, we compute the root multiplicities at level three for some hyperbolic Kac-Moody algebras including the basic hyperbolic extension of $A_1^{(1)}$ and $E_{10}$.10 pages, LaTeXHigh Energy Physics - TheoryQuantum Algebratext