GUNAWAN, H. On the angle between two subspaces of an inner product space. Hilbert Journal of Mathematical Analysis, [S. l.], v. 4, n. 1, p. 001–005, 2025. DOI: 10.62918/hjma.v4i1.48. Disponível em: https://hilbertjma.org/hilbertjma/article/view/48. Acesso em: 23 may. 2026.