What are the practical uses of Pythagorean Theorem? How to apply?

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.