2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148445This is my talk on the Bourbaki seminar, November 1996. It contains an elementary introduction to Borcherds' product formulas.16 pages, TeXAlgebraic GeometryProduct formulas for modular forms on O(2,n) (after R.Borcherds)text