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 2 widely used constant. formula_81 The (approximate) aspect ratio of paper sizes under ISO 216 (A4, A0, etc.) is 1:. This ratio of lengths of the shorter over the longer side guarantees that cutting a sheet in half along a line parallel to its shorter side results in the smaller sheets having the same (approximate) ratio as the original sheet. Proof: Let formula_82 shorter length and formula_83 longer length of the sides of a sheet of paper, with Let formula_85 be the analogue ratio of the halved sheet, then Square root of 2 The square root of 2, or the (1/2)th