structural:expansion, stylistic:style_transfer
The square root of 2 is the positive real number that, when multiplied by itself or squared, equals the number 2. It may be written in mathematics as 2 or 2 1 / 2. It is an algebraic number, and therefore not a transcendental number. Technically, it should be called the principal square root of 2, to distinguish it from the negative number with the same property. Geometrically, the square root of 2 is the length of a diagonal across a square with sides of one unit of length; this follows from the Pythagorean theorem. It was probably the first number known to be irrational. The fraction ⁠99/70⁠ is sometimes used as a good rational approximation with a reasonably small denominator. Sequence A002193 in the On-Line Encyclopedia of Integer Sequences consists of the digits in the decimal expansion of the square root of 2, here truncated to 65 decimal places:
  - 1.41421356237309504880168872420969807856967187537694807317667973799