At the beginning of China's earliest mathematical work "Parallel Calculation of Classics in Weeks", there is the relevant content of this theorem: Duke Zhou asked: "I heard that doctors are good at counting, so I want to ask the ancients to set the calendar of the week. The sky can't rise step by step, and the earth is unpredictable. How to calculate the number of people? " Shang Gao replied: "The counting method is based on a square, a circle is based on a square, a square is based on a moment, and the moment is 998 1. So the folded moment is considered as the product moment, which is half a moment outside the square, and the ring is a * * * disk. It's three, four, five, and two moments are 25 long. So it is called the product moment. "
The earliest documents in the west proved to be given by Pythagoras. It is said that when he proved Pythagorean theorem, he was ecstatic and killed a hundred cows to celebrate. Therefore, the western countries also call Pythagorean Theorem "Hundred Cows Theorem". Unfortunately, Pythagoras' proof method has long been lost, and we have no way of knowing his proof method.