 It follows that the variable "y" is inversely proportional to the variable "x" if there exists a non-zero constant "k" such that
or equivalently, formula_7 Hence the constant is the product of "x" and "y".The graph of two variables varying inversely on the Cartesian coordinate plane is a rectangular hyperbola.The product of the "x" and "y" values of each point on the curve equals the constant of proportionality ("k").