Pythagorean theorem

American  

noun

Geometry.

1. the theorem that the square of the hypotenuse of a right triangle is equal to the sum of the squares of the other two sides.

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Pythagorean theorem Scientific  

/ pĭ-thăg′ə-rē′ən /

1. A theorem stating that the square of the length of the hypotenuse of a right triangle is equal to the sum of the squares of the lengths of the other sides. It is mathematically stated as c ² = a ² + b ², where c is the length of the hypotenuse and a and b the lengths of the other two sides.

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Etymology

Origin of Pythagorean theorem

First recorded in 1905–10

Example Sentences

We still use the Pythagorean theorem and euclidean principles.

From Slate • Sep. 26, 2025

So what exactly is a trigonometric proof of the Pythagorean theorem, and why was Loomis so closed off to the idea?

From Scientific American • Apr. 10, 2023

Loomis believed that if you used these functions in a proof of the Pythagorean theorem, you would have assumed the theorem to begin with—a circular argument and thus an unforgivable mathematical error.

From Scientific American • Apr. 10, 2023

Fortunately, there’s a much easier way to use the Pythagorean theorem on a job site.

From Seattle Times • Dec. 12, 2022

I was drawn to the Pythagorean theorem and its promise of a universal—the ability to predict the nature of any three points containing a right angle, anywhere, always.

From "Educated" by Tara Westover