Microsoft® Excel® 2010 Formulas & Functions Inside Out

LOG()

Syntax. LOG(number,base)

Definition. This function returns the logarithm of a number to the given base.

Arguments

• number (required) The positive real number for which you want the logarithm.

• base (required) The base of the logarithm. If base is omitted, it is assumed to be 10.

Background. LOG() is the inverse function of EXP().

Example. The exponential function a = bx can use the logarithm as follows:

x = log_ba

The logarithm of a product (quotient) is the sum (difference) of the logarithms from the factors (dividend and divisor):

lg(a b) = lg a + lg b

lg(a : b) = lg a – lg b

Logarithms return:

• Multiplication and division to addition and subtraction.

• Exponentiation and root extraction to multiplication and division.

Logarithms simplify calculations with ...