the.com/pythagorean theorem

means In a right triangle, the square of the hypotenuse's length equals the sum of the squares of the other two sides' lengths (a² + b² = c²).

from Named for Pythagoras, the 6th-century BCE Greek philosopher-mathematician whose school in southern Italy treated numbers as near-sacred, though the relationship itself was known and used well before him — Babylonian clay tablets show the same number patterns over a thousand years earlier, and Indian and Chinese mathematicians arrived at versions of it independently. Pythagoras (or more likely his followers, since he left no writings himself) gets credit in the West chiefly because Greek tradition attached his name to a general proof, turning a practical surveyor's trick into a piece of formal geometry.