For example:
Logarithmic function is the inverse of power function. Y = 2 x is a power function. The inverse function of y = 2 x is x=log2y.
Definition of logarithm
If, that is, the x power of a is equal to n (a >; 0, and a≠ 1), then the number x is called the logarithm of n with a as the base, and is recorded as. Where a is called the base of logarithm, n is called real number, and x is called "logarithm with base of n".
1. In particular, we call the logarithm with the base of 10 the common logarithm and record it as lg.
2. Logarithm based on irrational number e (e=2.7 1828 ...) is called natural logarithm, and is recorded as ln.
3. Zero has no logarithm.
4. In the range of real numbers, negative numbers have no logarithm. [3]? In the range of complex numbers, negative numbers are logarithms.
Actually, if there is e(2k+ 1)πi+ 1=0, then ln(- 1) = (2k+1) π i has many periodic values, so that any negative number. For example: ln(-5)=(2k+ 1)πi+ln 5.