Mathematical economics is not a distinct branch of economics in the sense that public finance or international trade is. Rather, it is an approach to economic analysis, in which the economist makes use of mathematical symbols in the statement of his problem and also draws upon known mathematical theorems to aid in his reasoning. As far as the specific subject matter of analysis goes, it can be micro- or macroeconomic theory, or public finance, or the economics of underdeveloped countries, or what not.