The document demonstrates that the complex numbers (C) can be treated as a vector space isomorphic to R^2, thereby establishing that the dimension of C is 2. It constructs a linear map from C to R^2 by mapping a complex number z = x + iy to the ordered pair (x, y). The proof shows the isomorphism is both one-to-one and onto, affirming the relationship and the significance of graphing complex numbers in the xy-plane.