The logarithmic function lg is a logarithm (common logarithm) based on 10, such as lg 10= 1. In mathematics, logarithm is the inverse of power, just as division is the reciprocal of multiplication, and vice versa. This means that the logarithm of a number is an exponent that must produce another fixed number (radix). In a simple example, the logarithmic count factor in the multiplier. More generally, the power operation allows any positive real number to be raised to any power, and always produces positive results, so the logarithm of any two positive real numbers b and x whose b is not equal to 1 can be calculated.

Extended data:

Before the invention of logarithm, people were familiar with the method of converting the product of trigonometric functions into the sum or difference of trigonometric functions. German mathematician M.Stifel (about 1487- 1567) expounded the following correspondence in Comprehensive Arithmetic (1544):

This relationship can be summarized as follows

At the same time, the operational nature of this relationship (that is, the multiplication, division, power and root of the upper row number correspond to the addition, subtraction, multiplication and division of the lower row number) has also been widely known. After years of research on the operation system, Napier published the Explanation of the Wonderful Logarithm Law in 16 14, in which the logarithmic method was expounded in geometric terms with the help of kinematics.

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