square root of 2

The square root of 2, also known as Pythagoras' constant, often denoted by is the positive real number that, when multiplied by itself, gives the number 2. Its numerical value approximated to 65 decimal places  is:1.41421 35623 73095 04880 16887 24209 69807 85696 71875 37694 80731 76679 73799.The square root of 2 was probably the first known irrational number. Geometrically, it is the length of a diagonal across a square with sides of one unit of length; this follows from the Pythagorean theorem. On basic calculators with no square root function, the quick approximation for the square root of two is better than the quick approximation for pi, probably the most widely known irrational number.
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