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The diagonal of a square cannot be written as a fraction of its side, and the Greeks proved it.

Mathematics Facts, sourced to Wolfram MathWorld.

What it means

Assume it can, in lowest terms, and a short argument shows that both the top and the bottom of the fraction must be even, which contradicts the assumption. The discovery was a genuine shock to a school of thought built on the idea that all quantities are ratios of whole numbers, and the story that its discoverer was drowned at sea for it is almost certainly a later invention.

The claim comes from Wolfram MathWorld, and the page it comes from was read on 2026-08-27 to confirm it still says this.

This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.

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This fact is a cryptogram here: 75 letters over 21 different ones, graded medium.

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