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If the n power of A is equal to x(a is greater than 0, and A is not equal to 1), then the number N is called the logarithm of X with the base of A, and is recorded as n=㏒ax, where A is called the base of logarithm, X is called a real number, and N is called "the logarithm of X with the base of A".

In particular, we call the logarithm with the base of 10 the common logarithm, and call it lg.

Logarithms based on irrational number e (e=2.7 1828 ...) are called natural logarithms and recorded as ln.

Reference file: /view/356.htm