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 to converge. In linear algebra and operator theory, given a bounded positive semidefinite operator (a non-negative operator) "T" on a complex Hilbert space, "B" is a square root of "T" if "T" = "B* B", where "B*" denotes the Hermitian adjoint of "B". According to the spectral theorem, the continuous functional calculus can be applied to obtain an operator "T" such that "T" is itself positive and ("T") = "T". The operator "T" is the unique non-negative square root of "T". A bounded non-negative operator on a complex Hilbert space is self adjoint by definition. So "T" = ("T")* "T".