1. The problem statement, all variables and given/known data Prove GL(R) is not isomorphic to GL(C) 2. Relevant equations 3. The attempt at a solution Well I don't really have a good grasp of the issue at hand as this is another appendix problem, but my thoughts are I think GL(R) is a subgroup of GL(C) so maybe I could show they don't have the same cardinality? Would that be enough? Been a while since I did algebra... Not sure how I would would show that either.