Publisher Summary This chapter focuses on Cartesian products. It presents the theorem that states that the Cartesian product of two topological spaces in mathematics is a topological space. The chapter also provides an overview of projections and continuous mappings and presents a proof of the theorems that state that the projections are continuous mappings and very continuous mapping of two variables is continuous relative to each variable. In other words, if f: X × Y → W is continuous and if y0 ∈ Y, then the mapping f: X → W defined by the condition f1 (x) =f(x, yo) is continuous.