An Integral which has either or both limits Infinite or which has an Integrand which approaches Infinity at one or more points in the range of integration.
See also Definite Integral, Indefinite Integral, Integral, Proper Integral
Press, W. H.; Flannery, B. P.; Teukolsky, S. A.; and Vetterling, W. T. ``Improper Integrals.'' §4.4 in
Numerical Recipes in FORTRAN: The Art of Scientific Computing, 2nd ed. Cambridge, England:
Cambridge University Press, pp. 135-140, 1992.