Now, we are used to using radical symbols (such as etc. ) and find it 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, the dot 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, 8. However, 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 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 radical sign "". In a book, Descartes wrote: "If you want to find the square root of, write it;" If you want to find a cube root, write it. "

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 current cube root symbol appeared very late, and it was not until the eighteenth century that we saw the use of symbols in a book, such as the cube root of 25. Later, radical symbols in the form of "Ru" gradually began to be used.

This shows how difficult it is to adopt a symbol universally. It is the result of long-term continuous improvement, selection and elimination. It is the crystallization of the collective wisdom of several scholars, not invented by one person out of thin air, nor did it fall from the sky.

The root sign is in the form of √ in the computer.