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 formulas that give up to four square roots, if the matrix has any roots. If is a diagonal "n" × "n" matrix, one can obtain a square root by taking a diagonal matrix , where each element along the diagonal is a square root of the corresponding element of . If the diagonal elements of "D" are real and non-negative, and the square roots are taken with non-negative sign, the matrix will be the principal root of . If a matrix is idempotent, one of its square roots is the matrix itself. An "n" × "n" matrix is diagonalizable if