Later, someone improved it into a seven-table banquet. According to the number of people who eat, the table can be put together in different shapes, such as three people putting together a triangle, four people putting together a square and six people putting together a hexagon ... so that everyone is convenient and the atmosphere is better.
Later, someone reduced the banquet to only seven boards, used it to puzzle and turned it into a toy. Because it is very clever and interesting, people call it "Tangram".
In the late Ming and early Qing dynasties, people in the palace often used it to celebrate festivals and entertainment, and put all kinds of auspicious patterns and words together. The Palace Museum still keeps the puzzles of that time!
/kloc-in the 0/8th century, the jigsaw puzzle spread abroad, which immediately aroused great interest. Some foreigners played all night and called it "Tangtu", which means "Puzzle from China".
Interesting Pythagorean Theorem
Anyone who has studied geometry knows Pythagorean theorem. It is an important theorem in geometry and is widely used. So far, there are more than 400 ways to prove Pythagorean theorem. Among them, Garfield, the twentieth president of the United States, was told a story in the history of mathematics.
Why did the president think of proving Pythagorean theorem? Is he a mathematician or a math lover? The answer is no. Here's the story.
The discovery of Pythagoras
1876 One weekend evening, on the outskirts of Washington, D.C., a middle-aged man was walking and enjoying the beautiful scenery in the evening. He was a party member in * * * Ohio and Garfield. As he was walking, he suddenly found two children talking about something on a small stone bench nearby, arguing loudly and discussing in a low voice. Curious, Garfield followed the sound and walked to the two children. I wonder what these two children are doing. I saw a little boy bend down and draw a right triangle on the ground with branches. So Garfield asked them what they were doing.
The little boy said without looking up, "Excuse me, sir, if the two right angles of a right triangle are 3 and 4 respectively, what is the length of the hypotenuse?" Garfield replied, "It's 5." The little boy asked again, "If the two right angles are 5 and 7 respectively, what is the length of the hypotenuse of this right triangle?" Garfield replied without thinking, "The square of the hypotenuse must be equal to the square of 5 plus the square of 7." The little boy added, "Sir, can you tell the truth?" Garfield is speechless, unable to explain, and has a bad psychology.
So Garfield stopped walking and immediately went home to discuss the problems left by the little boy. After repeated thinking and calculation, he finally figured it out and gave a concise proof method.
On April 1876, Garfield published his proof of Pythagorean theorem in the New England Journal of Education.
188 1 year, Garfield became the twentieth president of the United States. Later,
Pythagoras' proof
In order to commemorate his intuitive, simple, understandable and clear proof of Pythagorean theorem, people call this proof "presidential proof".
Pythagorean theorem is also one of the most widely used theorems in mathematics. For example, starting from Pythagorean theorem, square roots and square roots are gradually developed; Finding pi by pythagorean theorem. It is said that the four right angles at the bottom of the pyramid are determined by this relationship. It is still used to pay off and "return to the square", that is, right-angle pay-off.
Because of this, it is not surprising that people admire this theorem. Greece issued a stamp on 1955. The design consists of three chessboards. This stamp commemorates the Pythagorean School, a school and religious group in Greece 2,500 years ago, its establishment and its cultural contribution. The design on the stamp is an explanation of Pythagorean theorem. The proof method displayed on Greek stamps was first recorded in Euclid's Elements of Geometry.
Nicaragua issued a set of ten commemorative stamps at 197 1 with the theme of "the ten most important mathematical formulas in the world", one of which is Pythagorean theorem.
In 2002, the World Congress of Mathematicians was held in Beijing, China, which was the first gathering of mathematicians in the 2/kloc-0 century. The symbol of this congress chose the "string diagram" to verify Pythagorean theorem as the central pattern, which can be said to fully display the achievements of ancient mathematics in China and fully promote the ancient mathematics culture in China. In addition, through hard work, China finally won the right to host the 2002 Mathematicians' Congress, which is also the development of mathematics in China by the international mathematics community.
Today, almost no one in the world doesn't know puzzles and puzzles. In foreign countries, it is called "Tangram", which means China map (not a map invented in the Tang Dynasty). Perhaps the history of Tangram can be traced back to Zhou Pian Shu Jing, an ancient book in pre-Qin China, which used square cutting to prove the Pythagorean theorem. At that time, the big square was cut into four identical triangles and a small square, that is, a string diagram, not a puzzle. Now the jigsaw puzzle has gone through a historical evolution.
The fun of Pythagoras
It was even suggested that a large device should be built on the earth to show the visiting whispers that there is intelligent life on the earth. The most suitable device is a huge figure symbolizing Pythagorean theorem, which can be located in the Sahara desert, Siberia in the Soviet Union or other vast wasteland. Because all knowledgeable creatures must know this extraordinary theorem, outsiders can easily recognize it as a sign! ?
Interestingly, except for the ternary quadratic equation x2+y2 =z2 (where X, Y and Z are unknowns), other ternary quadratic equations Xn+Yn = Zn (where N is a known positive integer and N > 2) cannot have positive integer solutions. This theorem is called Fermat's last theorem (Fermat was a French mathematician in17th century).