1. The problem statement, all variables and given/known data Let A be an m x n matrix, and suppose there exist n x m matrices C and D such that CA = In and AD = Im. Prove that C = D. 2. Relevant equations 3. The attempt at a solution I think it's obvious that C=D=A^(-1). But I'm having trouble proving it since I cannot prove that A is a square matrix and I'm not sure how where to start trying to prove it if A is not square.