DefinitionRational functions, that are ratios of polynomials, are integrable in certain conditions by use of partial fraction decomposition, substitution, or contour integration. These methods convert these complicated rational functions to the form that is easier to integrate. Rational function integrals are important in advanced calculus, control theory, and signal processing applications. One common example: The integral of ∫(x=2 + 1)/x dx is solved through a partial fraction that leads to the integral of ∫(1/2) du = 1/2 [ln x2 + 1].