# Documentation/Calc Functions/IMLOG10

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IMLOG10

Add-in

## Summary:

Calculates the logarithm to the base 10 or common logarithm of a complex number.

## Syntax:

IMLOG10(ComplexNumber)

## Returns:

Returns a text string giving the complex number that is the common logarithm of the complex number passed as argument.

## Arguments:

ComplexNumber is a string (in quotation marks) representing a complex number in the form a+bi or a+bj, or a reference to a cell containing that string, which is the complex number for which the common logarithm is to be calculated. a and b are real numbers.

• If ComplexNumber does not have an imaginary part (b equal to 0), the real part can be passed to IMLOG10 as a number rather than a string.
• If both real and imaginary parts of ComplexNumber are 0, IMLOG10 reports an invalid argument error (Err:502).
• If ComplexNumber is not a valid complex number, IMLOG10 reports an invalid argument error (Err:502).

## Additional details:

### Details specific to IMLOG10 function

For a complex number of the form a+bi, the common logarithm is given by the following equation:

IMLOG10(“a+bi”) = 0.434294481903251828 * IMLN(“a+bi”)

The value 0.434294481903251828 is the common logarithm of the mathematical constant e, which is known as Euler's number and has a value of approximately 2.71828.

### General information about Calc's handling of complex numbers

 Note: For convenience, the information in this subsection is repeated on all pages describing functions that manipulate complex numbers.
• A complex number is a number that can be expressed in the form a+bi, where a and b are real numbers and i is a symbol for the imaginary unit, such that i2=−1. a is known as the real part of the complex number and b is known as its imaginary part.
• In some disciplines using i to indicate the imaginary unit may be undesirable and, in such cases, the symbol j may be used instead. The functions provided by Calc to process complex numbers can use either i or j.
• For additional general background information, visit Wikipedia’s Complex number page.
• Within Calc, a complex number is represented as a string expression of the form "a+bi" or "a+bj", where a and b are real numbers. If the complex number happens to be a real number (b=0), then it can be represented as either a string expression or a numeric value. Complex number string expressions should not contain any space characters. Examples of valid Calc complex numbers include "2", -6, "2+3i", "3j", "12.34+56.78i", and "1e+23-1e-22j". Calc would not recognize the strings "1+j2", "i+1", and "i+j" as valid complex numbers.
• The representation of the complex numbers in strings can have up to 15 significant digits and scientific style is automatically used if needed (visit Wikipedia’s Scientific notation page for more information). The decimal delimiter in complex number string expressions is always a dot, irrespective of locale setting.

## Examples:

Formula Description Returns
=IMLOG10("1.2-3.4j") Here the function calculates the common logarithm of a complex number that has non-zero real and imaginary parts. 0.556971676153418-0.534835266713002j
=IMLOG10("-i") Here the function calculates the common logarithm of a complex number that has no real part. The result has no real part. -0.682188176920921i
=IMLOG10(-1) Here the function calculates the common logarithm of a complex number that has no imaginary part. The result has no real part. 1.36437635384184i
=IMLOG10("-1e20-i") Here the function calculates the common logarithm of a complex number that has non-zero real and imaginary parts. 20-1.36437635384184i
=IMLOG10(F1) where cell F1 contains the complex number 2-3j. Here the function calculates the common logarithm of a complex number that is entered in a cell. 0.556971676153418-0.426821890855467j

IMLOG10