1. A method for performing a digital signal processing calculation, the method employing a look-up table in which predetermined numerical values have been stored, wherein the numerical values are inverse values of square roots of numbers; the look-up table is searched for the inverse value of the square root of a desired number; if the inverse value of the square root of the desired number is found in the look-up table, the inverse value of the square root of the number is retrieved from the look-up table; if the inverse value of the square root of the desired number is not found in the look-up table, the number is scaled such that the inverse value of the square root of the scaled number is found in the look-up table; the inverse value of the square root of the scaled number is retrieved from the look-up table; the inverse value of the square root of the scaled number is descaled to produce the inverse value of the square root of the number; the inverse value of the square root of the number is used to carry out a calculation.