Kamaraj, K.Johnson, P.S.Athira, S.K.2026-02-042023Filomat, 2023, 37, 3, pp. 699-7093545180https://doi.org/10.2298/FIL2303699Khttps://idr.nitk.ac.in/handle/123456789/22175In this paper, necessary and sufficient conditions are given for the existence of Moore-Penrose inverse of a product of two matrices in an indefinite inner product space (IIPS) in which reverse order law holds good. Rank equivalence formulas with respect to IIPS are provided and an open problem is given at the end. © 2023, University of Nis. All rights reserved.Indefinite inner product spaceMoore-Penrose inverseReverse order lawWeighted generalized inverse