Square Root Day September 9, 1981 (9/9/81). Gordon remains the holiday's publicist, sending news releases to world media outlets. Gordon's daughter set up a Facebook group where people can share how they were celebrating the day. One suggested way of celebrating the holiday is by eating square radishes, or other root vegetables cut into shapes with square cross sections (thus creating a "square root"). Square Root Day occurs on the following dates each century: The number of years between consecutive Square Root Days in a century are consecutive odd numbers: 3, 5, 7, 9, 11, 13, 15, 17. This illustrates the fact that
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