Critical points of maps f:R^n-->R^m , m>1 Hi, Everyone: I am having trouble figuring out what the critical points would be for any such map f:R^n -->R^m , m>1. Problem is that I know sufficient conditions for differentiability (partials exist and are continuous.) but not necessary ones. So our differential is given by an mxn matrix. In the case of n=m, we just want the Jacobian matrix to be invertible, but I am not clear on how to deal with this issue when n=/m. Any Hints, Please.? Thanks.