Square root of 2 the square root of two, with a reasonable small denominator, the fraction (≈ 1.4142857) is sometimes used. The sequence in the OEIS gives the numerical value for the square root of two, truncated to 65 decimal places: The Babylonian clay tablet YBC 7289 (c. 1800–1600 BC) gives an approximation of in four sexagesimal figures, , which is accurate to about six decimal digits, and is the closest possible three-place sexagesimal representation of : Another early close approximation is given in ancient Indian mathematical texts, the Sulbasutras (c. 800–200 BC) as follows: "Increase the length [of the side] by its third
Fast inverse square root The calculation of is based on the identity Using the approximation of the logarithm above, applied to both and , the above equation gives: Thus, an approximation of is: which is written in the code as The first term above is the magic number from which it can be inferred that . The second term, , is calculated by shifting the bits of one position to the right. With as the inverse square root, . The approximation yielded by the earlier steps can be refined by using a root-finding method, a method that finds the zero of a function. The