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 Square root of a matrix In mathematics, the square root of a matrix extends the notion of square root from numbers to matrices. Matrix is said to be a square root of if the matrix product is equal to . In general, a matrix can have several square roots. For example, the matrix formula_1 has square roots formula_2 and formula_3, as well as their additive inverses. Another example is the 2×2 identity matrix formula_4 which has infinitely many symmetric rational square roots given by where formula_6 is any Pythagorean triple—that is, any set of positive integers such that formula_7. However,