Pythagorean theorem is widely used by engineers and technicians. For example, the roof structure of rural houses can be calculated by Pythagorean theorem, which is also used in designing engineering drawings. Pythagorean theorem can be used in finding data related to circles and triangles.
It is also widely used in physics, such as finding several forces, or the speed and direction of object motion.
In ancient times, it was mostly used in engineering, such as building houses, repairing wells and making cars.
? Example 1:
Another ancient book in the Warring States period in China, Twelve Notes on the Postscript of the History of the Road, recorded this: "Yu ruled the flood and decided to flow in the rivers, watching the shape of mountains and rivers, and decided to compete. In addition to catastrophic disasters, the East China Sea is flooded and there is no danger of drowning. " In order to control the flood, Dayu decided the direction of the water flow according to the height of the terrain, guided the situation to make the flood flow into the sea, so that there would be no more flood disaster. This is the result of applying Pythagorean theorem.
Example 2:
In home decoration, in order to judge whether an angle is a standard right angle, workers can measure 30 cm and 40 cm from this angle to two walls and mark them on a point, and then measure whether the distance between these two points is 50 cm. If a certain error is exceeded, the angle is not a right angle.
For example, at point A, there is a very high pole nearby, and at point B, the rope pulled out from the top of the pole should be fixed at this point. You can calculate the length requirement of the rope.
Example 3:
When doing carpentry, if there is a large piece of wood to set a right angle, use Pythagorean theorem. The square is too small, and the right angle error of the painting on the big board is large. When working as a welder, Pythagorean theorem is also used for large frames and must be at right angles. For example, if I want a right angle, take the side of the right angle as 3 meters long, the side of the right angle as 4 meters long, and let the hypotenuse be 5 meters, then this angle is a right angle.
The origin of Pythagorean theorem;
Zhou's Parallel Computation Classic says that this theorem has been preliminarily applied in actual measurement. This book also records that a mathematician named Chen Zi used this theorem to measure the height of the sun, the diameter of the sun and the length and width of heaven and earth.
Egyptians 5000 years ago also knew the special cases of this theorem, namely hook 3, strand 4 and chord 5, and used it to determine the right angle. Later, it was gradually extended to the general situation. At the bottom of the pyramid, four corners are square, pointing east, west, north and south respectively. The visible direction is very accurate, and all four corners are strictly right angles. Of course, measuring a right angle can be used as a perpendicular method, but if the Pythagorean theorem is reversed, that is, as long as the three sides of a triangle are 3, 4, 5, or conform to the formula, then the angle opposite to the chord side must be a right angle. In 540 BC, the Greek mathematician Pythagoras noticed that this relationship existed when the three sides of a right triangle were 3, 4, 5, or 5, 12, 13 respectively. He thought: Do all three sides of a right triangle conform to this law? Conversely, if all three sides conform to this rule, is it a right triangle?
He collected many examples, all of which answered these two questions in the affirmative. He was so happy that he killed a hundred cows to congratulate him.
Later, westerners called this theorem Pythagoras theorem.
reference data
Ginger. A new classical theory of parallel computing. Shanghai: Shanghai Jiaotong University Press, 2065438+June 2005 &; # 160;