√2 stands for the arithmetic square root of 2. Generally speaking, if the square of a nonnegative x equals a, that is, x? =a, then this number x is called the arithmetic square root of a.
The root number (arithmetic square root) originated from the diagonal length of the square "root number two", and the discovery of this "root number two" once caused the Pythagorean school to panic. Because according to the authoritative explanation at that time (that is, the Pythagorean school theory), everything is counted (that is, everything in the world can be represented by rational numbers)
For this irrational number "root number two", people finally choose to use the root number to represent it.
Extended data:
The origin of root number two:
In 500 BC, hippasus, a disciple of Pythagoras School, discovered an amazing fact: the diagonal of a square is incommensurable with the length of one side (if the side length of a square is 1, the length of the diagonal is not a rational number), which is quite different from Pythagoras School's philosophy of "everything is a number" (referring to a rational number).
This discovery frightened the leaders of the school, thinking that it would shake their dominant position in the academic world, so they tried their best to stop the spread of this truth, and Herbesos was forced into exile. Unfortunately, he met his disciples on a seagoing ship. Was brutally thrown into the water by Pisces disciples and killed. Thus began the history of science, but it was a tragedy.