In mathematics, if a number B is the n-th root of a number, then BN = A. When referring to the n-th root of a real number, assume that you want the main n-th root of this number, which is represented by a root sign. A unique real number B, whose principal n-th root is the n-th root of A, has the same sign as A. Note that if n is an even number, negative numbers will have no principal n-th root. The square root is called the square root and the cube root is called the cube root.

English: radical symbols

Now, we are used to using the root sign (such as √). ), and I think it is simple and convenient to use.

Then, how did the radical sign come into being and evolve into what it is now?

In ancient times, Egyptians used the symbol ┌ to represent the square root. Indians write ka in front of the square root number. Used by Arabs. Around 1840, the Germans used the dot "."to represent the square root, two dots "…" to represent the square root of degree 4, and three dots "…" to represent the cube root. For example, .3, ...3, ... 3 represent the square root, quartic square root and cubic root of 3, respectively. By the beginning of the16th century, perhaps because of the fast writing speed, dots had a slender tail and became "-". 1525, Rudolf adopted the radical sign for the first time in his algebra works. For example, he wrote that √4 is 2, √9 is 3, and it is represented by √8 and √8, but this writing method has not been generally recognized and adopted.

At the same time, some people use the capital r of the first letter of the Latin root of the word "root" to indicate the square operation, and then use the first letter q of the Latin word "square" or the first letter c of the "cube" to indicate how many times the square has been opened. For example, at that time, someone wrote R.q.4352, and now it can be written as R.C. using the symbol of mathematician Bunbury (1526-1572). 7p。 "where, R.q. 14╜? ╜ "is equivalent to the brackets used today, and p (plus sign) is equivalent to the plus sign used today (at that time, even the addition and subtraction signs"+"and"-"were not universal).

It was not until17th century that the French mathematician Descartes (1596-1650) first used the root sign "√" which is still in use today. Descartes wrote in a book: "If you want to find the square root of n, write √n, and if you want to find the cubic root of n, write 3 √ n (superscript 3)."

What is the consideration? Sometimes, many terms have been squared. In order to avoid confusion, Descartes connected these terms with a horizontal line, and put the root sign √ in front of them (but there is a small hook more than Rudolph's root sign), which is the current form of root sign.

The present symbol of cube root appeared very late, and it was not until18th century that the symbol 3 √ (superscript 3) was used in a book. For example, the cube root of 25 is represented by 3 √ 25 (superscript 3). Later, radical symbols in the form of √ gradually began to be used. ...

This shows how difficult it is for a symbol to be widely used. It is the result of continuous improvement, selection and elimination for a long time. It is the crystallization of the collective wisdom of mathematicians, not invented by one person out of thin air, and will never fall from the sky.

The root number in the computer is √. You can press AIT and press 4 1420 in sequence at the same time. Of course, it can't be used in QQ or Word.