In ancient China, the short right-angled side was called a hook, the long right-angled side was called a chord, and the hypotenuse was called a chord. According to the book Zhou Bi Shu Jing in the Western Han Dynasty in China, about 1 100 BC, people already know that if the hook is three and the strand is four, then the string is five.
The inscribed circle diameter of a triangle with three strands, four chords and five right angles is 2. Therefore, there is a saying of "hooking three strands, four strings, five diameters and two".
Pythagorean Theorem Abroad
The ancient Babylonians knew and applied Pythagorean theorem as early as around 3000 BC, and they also knew many Pythagorean sequences. There is an ancient Babylonian clay tablet numbered "Printon 322" in the library of Columbia University in the United States, on which a large number of checkers are recorded. The ancient Egyptians also used Pythagorean theorem when building magnificent pyramids and measuring the land after the Nile flooded.
In the 6th century BC, the Greek mathematician Pythagoras proved the Pythagorean theorem, so westerners used to call it Pythagorean theorem.
In the 4th century BC, the Greek mathematician Euclid gave a proof in the Elements of Geometry (Volume I, Proposition 47).
On April 1876 and 1 day, Garfield published his proof of Pythagorean theorem in the New England Journal of Education.
The Pythagorean proposition was published in 1940, and 367 different proofs were collected.