Square Root of 2

The square root of 2 is the positive real number that equals 2 when multiplied by itself, with an approximate value of 1.4142. It was probably the first number ever shown to be irrational, meaning it cannot be written as a ratio of two integers, and geometrically it is the length of the diagonal of a unit square, a fact following from the Pythagorean theorem. The Pythagoreans discovered this irrationality by studying the relationship between a square's diagonal and its side, a finding with significant philosophical consequences for how numbers were understood, and the constant is sometimes called Pythagoras's number or Pythagoras's constant in recognition of that history. It also shows up in practical contexts far from pure mathematics, including international paper sizing standards, musical intervals and photographic aperture ratios. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/