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Theorem

Pythagorean Theorem

Also Known As Pythagoras' Theorem
Geometry

Perhaps the most famous theorem in mathematics, relating the three sides of a right triangle. Tablets from Babylon show the relationship was known and used numerically well over a thousand years before Pythagoras; tradition credits his school with the first general geometric proof, though no writing survives to confirm this directly. Hundreds of distinct proofs are now known, including one attributed to United States President James A. Garfield.

Facts
Disputed
Proof Year
520 BCE 2
The relationship was used empirically by Babylonian and Egyptian mathematicians centuries earlier; whether Pythagoras personally, or a later member of his school, produced the first general proof is genuinely uncertain, since no writing by Pythagoras survives.
Statement
In a right triangle, the square of the length of the hypotenuse equals the sum of the squares of the lengths of the other two sides: a squared plus b squared equals c squared. 1
Classification
Statement Form
Identity or Equation 1
FAQs

Did Pythagoras discover the Pythagorean theorem?

The relationship was known to the Babylonians about 1000 years earlier; Pythagoras may have been the first to prove it.

Not in the sense of first knowing the relationship. The history of mathematics at St Andrews notes that the theorem now known as Pythagoras's theorem was known to the Babylonians 1000 years earlier, but that Pythagoras may have been the first to prove it. So the name reflects a tradition of credit for a general proof rather than a first sighting of the numerical fact.
Connections

Has Statement Form

Equation, Concepts
Identity, Concepts

In Branch

Source Wolfram MathWorld
Additional Source Pythagorean Theorem (Wikipedia)Introduction

Proved By

Pythagoras, Mathematicians

Why this is disputed. Traditional attribution; independently confirmed proof authorship is not possible given the surviving record.

Source MacTutor History of Mathematics Archive
Additional Source Pythagorean Theorem (Wikipedia)History section
Sources
1. Wolfram MathWorld
Wolfram Research, Inc.View the Source
2. MacTutor History of Mathematics Archive
University of St Andrews, School of Mathematics and StatisticsBiography of Pythagoras
Quote, Biography of Pythagoras
Although the theorem, now known as Pythagoras's theorem, was known to the Babylonians 1000 years earlier he may have been the first to prove it.
View the Source
Pythagorean Theorem (Wikipedia)
Wikimedia Foundation
  • Proved By: Pythagoras, History section
    The theorem is named for the Greek philosopher Pythagoras, born around 570 BC.
  • In Branch: Geometry, Introduction
    the Pythagorean theorem or Pythagoras's theorem is a fundamental relation in Euclidean geometry between the three sides of a right triangle.
View the Source
Dissenting Readings (1 dissenting reading)
Proved By: Pythagoras

Crediting Pythagoras alone with this theorem understates its independent discovery elsewhere. Chinese mathematical texts, most notably the Zhoubi Suanjing, preserve an independent geometric derivation of the same right-triangle relationship, there called the gougu theorem, on a timeline that historians of Chinese science place at or before the period conventionally assigned to Pythagoras, alongside the already-acknowledged Babylonian numerical knowledge of the relationship a thousand years earlier still. The theorem was discovered and used in more than one civilization independently; naming it for one Greek school, while a durable convention, is a convention, not a finding about priority.

A dissenting reading, from Joseph NeedhamMacTutor History of Mathematics Archive, University of St Andrews, School of Mathematics and Statistics

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