If a n = b (a > 0, and a≠ 1), the number n is called the logarithm of b with a base, and it is called n = log (a) b, where a is a subscript, a is called "base" and b is called "true number".

In general, the function y = logax(a >；; 0, and a≠ 1) is called logarithmic function, that is, a function with power (real number) as independent variable, exponent as dependent variable and base constant as constant is called logarithmic function.

Where x is the independent variable and the domain of the function is (0, +∞), that is, x >；; 0。 It is actually the inverse function of exponential function, which can be expressed as x=ay. Therefore, the stipulation of a in exponential function is also applicable to logarithmic function.

Extended data:

Special logarithm:

(1)ln. Logarithm with constant e as the base. Write lnn (n >; 0)。 It is of great significance in physics, biology and other natural sciences. The general representation is lnx. Logx is also commonly used in mathematics to represent natural logarithm.

(2)lg (logarithm based on 10) Logarithmic function lg is a logarithm based on 10 (common logarithm), such as lg 10= 1. Lg is log 10.

References:

Baidu encyclopedia-logarithm