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
Square root of a matrix finitely many terms will be non-zero and It suffices to check uniqueness for a Jordan block with λ = 1. The square constructed above has the form "S" = "I" + "L" where "L" is polynomial in "N" without constant term. Any other square root "T" with positive eigenvalues has the form "T" = "I" + "M" with nilpotent, commuting with "N" and hence "L". But then . Since "L" and commute, the matrix is nilpotent and is invertible with inverse given by a Neumann series. Hence "L" = . If is a matrix with positive eigenvalues and minimal polynomial