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1 x 1 =2

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"How can it equal one? If one times one equals one that means that two is of no value because one times itself has no effect. One times one equals two because the square root of four is two, so what's the square root of two? Should be one, but we're told its two, and that cannot be."

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Understanding Mathematics by Peter Alfeld, Department of Mathematics, University of Utah

Why is the square root of 2 irrational?

It was one of the most surprising discoveries of the Pythagorean School of Greek mathematicians that there are irrational numbers. According to Courant and Robbins in "What is Mathematics": This revelation was a scientific event of the highest importance. Quite possibly it marked the origin of what we consider the specifically Greek contribution to rigorous procedure in mathematics. Certainly it has profoundly affected mathematics and philosophy from the time of the Greeks to the present day.

Specifically, the Greeks discovered that the diagonal of a square whose sides are 1 unit long has a diagonal whose length cannot be rational. By the Pythagorean Theorem, the length of the diagonal equals the square root of 2. So the square root of 2 is irrational!

The following proof is a classic example of a proof by contradiction: We want to show that A is true, so we assume it's not, and come to contradiction. Thus A must be true since there are no contradictions in mathematics!


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