Square root of 2

The square root of 2, or the (1/2)th power of 2, written in mathematics as or , is the positive irrational number that, when multiplied by itself, equals the number 2. To be more correct, it is called the principal square root of 2, to tell it apart from the negative version of itself where that is also true.
Geometrically, the square root of 2 is the length of a diagonal across a square with sides with a length of one; this can be found with the Pythagorean theorem. Because of that, it is also called the Pythagoras's constant.
Proof that the square root of 2 is not rational.
The number formula_1 is not rational. Here is the proof.
Therefore, it is not true that formula_1 is a rational number. So formula_1 must be irrational.