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 multidigit numbers. Unlike the LN() and LOG10() functions, the LOG() function allows you to specify the base. If you don’t specify the base, the LOG() function equals LOG10().

See Also

EXP(), IMLN(), IMLOG10(), IMLOG2(), LN(), LOG10()

Sample Files

Use the LOG_LN and EXP_LOG_LN worksheets in the Chapter16.xls or Chapter16.xlsx sample file. The sample files are found in the Chapter16 folder. For more information about the sample files, see the section titled Using the Sample Files.