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Science Quote by Euclid

"In right-angled triangles the square on the side subtending the right angle is equal to the squares on the sides containing the right angle"

About this Quote

A right triangle is a humble shape, but Euclid turns it into a manifesto: reality can be made legible, even inevitable, through disciplined reasoning. This line is the Pythagorean theorem in its most austere, law-court phrasing. No mysticism, no origin myth, no appeal to authority. Just a claim about space that dares you to prove it.

The intent is not merely to hand students a handy formula. In Euclid's Elements, propositions like this are stress tests for a bigger project: building geometry from a small set of definitions and axioms, then showing that complex truths follow as cleanly as dominoes. The subtext is methodological bravado. Knowledge, Euclid implies, should be constructed so tightly that disagreement becomes a matter of error, not opinion. That confidence is also a kind of power: if you can demonstrate what must be true about triangles, you can imagine doing the same for architecture, astronomy, engineering, even governance.

Context matters. Euclid is writing in a Hellenistic world hungry for system and standardization, in a city (Alexandria) designed as an intellectual machine. The theorem itself was known in various forms before him, but Euclid's cultural innovation is packaging it as part of a coherent, reproducible apparatus. The phrasing "square on the side" points to a visual, geometric proof tradition: areas, not algebra, do the work. It's an argument you can draw, audit, and teach, which is precisely why it has endured: it scales from the sand table to the modern blueprint without changing its tone or its claim to certainty.

Quote Details

TopicReason & Logic
SourceEuclid, Phillips (1826). “Elements of Geometry, Containing the First Six Books of Euclid”, p.41
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Citation Formats

APA Style (7th ed.)
Euclid. (2026, February 14). In right-angled triangles the square on the side subtending the right angle is equal to the squares on the sides containing the right angle. FixQuotes. https://fixquotes.com/quotes/in-right-angled-triangles-the-square-on-the-side-185294/

Chicago Style
Euclid. "In right-angled triangles the square on the side subtending the right angle is equal to the squares on the sides containing the right angle." FixQuotes. February 14, 2026. https://fixquotes.com/quotes/in-right-angled-triangles-the-square-on-the-side-185294/.

MLA Style (9th ed.)
"In right-angled triangles the square on the side subtending the right angle is equal to the squares on the sides containing the right angle." FixQuotes, 14 Feb. 2026, https://fixquotes.com/quotes/in-right-angled-triangles-the-square-on-the-side-185294/. Accessed 15 Feb. 2026.

More Quotes by Euclid Add to List
Euclid on the Pythagorean Theorem: Geometry as Proof
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About the Author

Euclid

Euclid (325 BC - 270 BC) was a Scientist from Greece.

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